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  • Force close message when preferences are called via menu button

    - by Dan T
    I see no problem in the code. Help? preferences.xml <?xml version="1.0" encoding="utf-8"?> <PreferenceScreen xmlns:android="http://schemas.android.com/apk/res/android"> <ListPreference android:title="Gender" android:summary="Are you male or female?" android:key="genderPref" android:defaultValue="male" android:entries="@array/genderArray" android:entryValues="@array/genderValues" /> <ListPreference android:title="Weight" android:summary="How much do you weigh?" android:key="weightPref" android:defaultValue="180" android:entries="@array/weightArray" android:entryValues="@array/weightValues" /> </PreferenceScreen> arrays.xml <?xml version="1.0" encoding="utf-8"?> <resources> <string-array name="genderArray"> <item>Male</item> <item>Female</item> </string-array> <string-array name="genderValues"> <item>male</item> <item>female</item> </string-array> <string-array name="weightArray"> <item>120</item> <item>150</item> <item>180</item> <item>210</item> <item>240</item> <item>270</item> </string-array> <string-array name="weightValues"> <item>120</item> <item>150</item> <item>180</item> <item>210</item> <item>240</item> <item>270</item> </string-array> </resources> Preferences.java: package com.dantoth.drinkingbuddy; import android.os.Bundle; import android.preference.PreferenceActivity; public class Preferences extends PreferenceActivity { @Override protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); addPreferencesFromResource(R.xml.preferences); }; } butts.xml (idk why it's butts but I've gotten used to it now. really just sets up the menu button) <?xml version="1.0" encoding="utf-8"?> <menu xmlns:android="http://schemas.android.com/apk/res/android"> <item android:id="@+id/settings" android:title="Settings" android:icon="@drawable/ic_menu_settings" /> <item android:id="@+id/archive" android:title="Archive" android:icon="@drawable/ic_menu_archive" /> <item android:id="@+id/new_session" android:title="New Session" android:icon="@drawable/ic_menu_new" /> <item android:id="@+id/about" android:title="About" android:icon="@drawable/ic_menu_about" /> </menu> within DrinkingBuddy.java: @Override public boolean onOptionsItemSelected(MenuItem item) { switch (item.getItemId()) { case R.id.settings: startActivity(new Intent(this, Preferences.class)); return true; case R.id.archive: Toast.makeText(this, "Expect to see your old drinking sessions here.", Toast.LENGTH_LONG).show(); return true; //ETC. } return false; That's it. I can press the menu button on the phone and see the menu items I created, but when I click on the "Settings" (r.id.settings) it FC. Do I have to do anything to the manifest/other thing to get this to work??

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  • How can I turn a SimpleXML object to array, then shuffle?

    - by Joshua Cody
    Crux of my problem: I've got an XML file that returns 20 results. Within these results are all the elements I need to get. Now, I need to return them in a random order, and be able to specifically work with item 1, items 2-5, and items 6-17. Idea 1: Use this script to convert the object to an array, which I can shuffle through. This is close to working, but a few of the elements I need to get are under a different namespace, and I don't seem to be able to get them. Code: /* * Convert a SimpleXML object into an array (last resort). * * @access public * @param object $xml * @param boolean $root - Should we append the root node into the array * @return array */ function xmlToArray($xml, $root = true) { if (!$xml->children()) { return (string)$xml; } $array = array(); foreach ($xml->children() as $element => $node) { $totalElement = count($xml->{$element}); if (!isset($array[$element])) { $array[$element] = ""; } // Has attributes if ($attributes = $node->attributes()) { $data = array( 'attributes' => array(), 'value' => (count($node) > 0) ? xmlToArray($node, false) : (string)$node // 'value' => (string)$node (old code) ); foreach ($attributes as $attr => $value) { $data['attributes'][$attr] = (string)$value; } if ($totalElement > 1) { $array[$element][] = $data; } else { $array[$element] = $data; } // Just a value } else { if ($totalElement > 1) { $array[$element][] = xmlToArray($node, false); } else { $array[$element] = xmlToArray($node, false); } } } if ($root) { return array($xml->getName() => $array); } else { return $array; } } $thumbfeed = simplexml_load_file('http://gdata.youtube.com/feeds/api/videos?q=skadaddlemedia&max-results=20&orderby=published&prettyprint=true'); $xmlToArray = xmlToArray($thumbfeed); $thumbArray = $xmlToArray["feed"]; for($n = 0; $n < 18; $n++){ $title = $thumbArray["entry"][$n]["title"]["value"]; $desc = $thumbArray["entry"][0]["content"]["value"]; $videoUrl = $differentNamespace; $thumbUrl = $differentNamespace; } Idea 2: Continue using my working code that is getting the information using a foreach, but store each element in an array, then use shuffle on that. I'm not precisely sure hwo to write to an array within a foreach loop and not write over one another, though. Working code: foreach($thumbfeed->entry as $entry){ $thumbmedia = $entry->children('http://search.yahoo.com/mrss/') ->group ; $thumb = $thumbmedia->thumbnail[0]->attributes()->url; $thumburl = $thumbmedia->content[0]->attributes()->url; $thumburl1 = explode("http://www.youtube.com/v/", $thumburl[0]); $thumbid = explode("?f=videos&app=youtube_gdata", $thumburl1[1]); $thumbtitle = $thumbmedia->title; $thumbyt = $thumbmedia->children('http://gdata.youtube.com/schemas/2007') ->duration ; $thumblength = $thumbyt->attributes()->seconds; } Ideas on if either of these are good solutions to my problem, and if so, how I can get over my execution humps? Thanks so much for any help you can give.

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  • Peer did not return a certificate

    - by pfista
    I am trying to get two way SSL authentication working between a Python server and an Android client application. I have access to both the server and client, and would like to implement client authentication using my own certificate. So far I have been able to verify the server certificate and connect without client authentication. What sort of certificate does the client need and how do I get it to automatically send it to the server during the handshake process? Here is the client and server side code that I have so far. Is my approach wrong? Server Code while True: # Keep listening for clients c, fromaddr = sock.accept() ssl_sock = ssl.wrap_socket(c, keyfile = "serverPrivateKey.pem", certfile = "servercert.pem", server_side = True, # Require the client to provide a certificate cert_reqs = ssl.CERT_REQUIRED, ssl_version = ssl.PROTOCOL_TLSv1, ca_certs = "clientcert.pem", #TODO must point to a file of CA certificates?? do_handshake_on_connect = True, ciphers="!NULL:!EXPORT:AES256-SHA") print ssl_sock.cipher() thrd = sock_thread(ssl_sock) thrd.daemon = True thrd.start() I suspect I may be using the wrong file for ca_certs...? Client Code private boolean connect() { try { KeyStore keystore = KeyStore.getInstance("BKS"); // Stores the client certificate, to be sent to server KeyStore truststore = KeyStore.getInstance("BKS"); // Stores the server certificate we want to trust // TODO: change hard coded password... THIS IS REAL BAD MKAY truststore.load(mSocketService.getResources().openRawResource(R.raw.truststore), "test".toCharArray()); keystore.load(mSocketService.getResources().openRawResource(R.raw.keystore), "test".toCharArray()); // Use the key manager for client authentication. Keys in the key manager will be sent to the host KeyManagerFactory keyFManager = KeyManagerFactory.getInstance(KeyManagerFactory.getDefaultAlgorithm()); keyFManager.init(keystore, "test".toCharArray()); // Use the trust manager to determine if the host I am connecting to is a trusted host TrustManagerFactory trustMFactory = TrustManagerFactory.getInstance(TrustManagerFactory .getDefaultAlgorithm()); trustMFactory.init(truststore); // Create the socket factory and add both the trust manager and key manager SSLCertificateSocketFactory socketFactory = (SSLCertificateSocketFactory) SSLCertificateSocketFactory .getDefault(5000, new SSLSessionCache(mSocketService)); socketFactory.setTrustManagers(trustMFactory.getTrustManagers()); socketFactory.setKeyManagers(keyFManager.getKeyManagers()); // Open SSL socket directly to host, host name verification is NOT performed here due to // SSLCertificateFactory implementation mSSLSocket = (SSLSocket) socketFactory.createSocket(mHostname, mPort); mSSLSocket.setSoTimeout(TIMEOUT); // Most SSLSocketFactory implementations do not verify the server's identity, allowing man-in-the-middle // attacks. This implementation (SSLCertificateSocketFactory) does check the server's certificate hostname, // but only for createSocket variants that specify a hostname. When using methods that use InetAddress or // which return an unconnected socket, you MUST verify the server's identity yourself to ensure a secure // connection. verifyHostname(); // Safe to proceed with socket now ... I have generated a client private key, a client certificate, a server private key, and a server certificate using openssl. I then added the client certificate to keystore.bks (which I store in /res/raw/keystore.bks) I then added the server certificate to the truststore.bks So now when the client tries to connect I am getting this error server side: ssl.SSLError: [Errno 1] _ssl.c:504: error:140890C7:SSL routines:SSL3_GET_CLIENT_CERTIFICATE:peer did not return a certificate And when I try to do this in the android client SSLSession s = mSSLSocket.getSession(); s.getPeerCertificates(); I get this error: javax.net.ssl.SSLPeerUnverifiedException: No peer certificate So obviously the keystore I am using doesn't appear to have a correct peer certificate in it and thus isn't sending one to the server. What should I put in the keystore to prevent this exception? Furthermore, is this method of two way SSL authentication safe and effective?

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  • JUnit testing, exception in threa main

    - by Crystal
    I am new to JUnit and am trying to follow my prof's example. I have a Person class and a PersonTest class. When I try to compile PersonTest.java, I get the following error: Exception in thread "main" java.lang.NoSuchMethodError: main I am not really sure why since I followed his example. Person.java public class Person implements Comparable { String firstName; String lastName; String telephone; String email; public Person() { firstName = ""; lastName = ""; telephone = ""; email = ""; } public Person(String firstName) { this.firstName = firstName; } public Person(String firstName, String lastName, String telephone, String email) { this.firstName = firstName; this.lastName = lastName; this.telephone = telephone; this.email = email; } public String getFirstName() { return firstName; } public void setFirstName(String firstName) { this.firstName = firstName; } public String getLastName() { return lastName; } public void setLastName(String lastName) { this.lastName = lastName; } public String getTelephone() { return telephone; } public void setTelephone(String telephone) { this.telephone = telephone; } public String getEmail() { return email; } public void setEmail(String email) { this.email = email; } public int compareTo(Object o) { String s1 = this.lastName + this.firstName; String s2 = ((Person) o).lastName + ((Person) o).firstName; return s1.compareTo(s2); } public boolean equals(Object otherObject) { // a quick test to see if the objects are identical if (this == otherObject) { return true; } // must return false if the explicit parameter is null if (otherObject == null) { return false; } if (!(otherObject instanceof Person)) { return false; } Person other = (Person) otherObject; return firstName.equals(other.firstName) && lastName.equals(other.lastName) && telephone.equals(other.telephone) && email.equals(other.email); } public int hashCode() { return this.email.toLowerCase().hashCode(); } public String toString() { return getClass().getName() + "[firstName = " + firstName + '\n' + "lastName = " + lastName + '\n' + "telephone = " + telephone + '\n' + "email = " + email + "]"; } } PersonTest.java import org.junit.Test; // JDK 5.0 annotation support import static org.junit.Assert.assertTrue; // Using JDK 5.0 static imports import static org.junit.Assert.assertFalse; // Using JDK 5.0 static imports import junit.framework.JUnit4TestAdapter; // Need this to be compatible with old test driver public class PersonTest { /** A test to verify equals method. */ @Test public void checkEquals() { Person p1 = new Person("jj", "aa", "[email protected]", "1112223333"); assertTrue(p1.equals(p1)); // first check in equals method assertFalse(p1.equals(null)); // second check in equals method assertFalse(p1.equals(new Object())); // third chk in equals method Person p2 = new Person("jj", "aa", "[email protected]", "1112223333"); assertTrue(p1.equals(p2)); // check for deep comparison p1 = new Person("jj", "aa", "[email protected]", "1112223333"); p2 = new Person("kk", "aa", "[email protected]", "1112223333"); assertFalse(p1.equals(p2)); // check for deep comkparison } }

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  • Why does windows XP minimize my swing full screen window on my second screen ?

    - by Laurent K
    Hello dear fellows, In the application I'm developping (in Java/swing), I have to show a full screen window on the second screen of the user. I did this using a code similar to the one you'll find below... Be, as soon as I click in a window opened by windows explorer, or as soon as I open windows explorer (i'm using windows XP), the full screen window is minimized... Do you know any way or workaround to fix this problem, or is there something important I did not understand with full screen windows? Thanks for the help, import javax.swing.JFrame; import javax.swing.JPanel; import javax.swing.JWindow; import java.awt.BorderLayout; import java.awt.Dimension; import java.awt.GraphicsDevice; import java.awt.GraphicsEnvironment; import java.awt.Window; import javax.swing.JButton; import javax.swing.JToggleButton; import java.awt.Rectangle; import java.awt.GridBagLayout; import javax.swing.JLabel; public class FullScreenTest { private JFrame jFrame = null; // @jve:decl-index=0:visual-constraint="94,35" private JPanel jContentPane = null; private JToggleButton jToggleButton = null; private JPanel jFSPanel = null; // @jve:decl-index=0:visual-constraint="392,37" private JLabel jLabel = null; private Window window; /** * This method initializes jFrame * * @return javax.swing.JFrame */ private JFrame getJFrame() { if (jFrame == null) { jFrame = new JFrame(); jFrame.setSize(new Dimension(474, 105)); jFrame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE); jFrame.setContentPane(getJContentPane()); } return jFrame; } /** * This method initializes jContentPane * * @return javax.swing.JPanel */ private JPanel getJContentPane() { if (jContentPane == null) { jContentPane = new JPanel(); jContentPane.setLayout(null); jContentPane.add(getJToggleButton(), null); } return jContentPane; } /** * This method initializes jToggleButton * * @return javax.swing.JToggleButton */ private JToggleButton getJToggleButton() { if (jToggleButton == null) { jToggleButton = new JToggleButton(); jToggleButton.setBounds(new Rectangle(50, 23, 360, 28)); jToggleButton.setText("Show Full Screen Window on 2nd screen"); jToggleButton.addActionListener(new java.awt.event.ActionListener() { public void actionPerformed(java.awt.event.ActionEvent e) { showFullScreenWindow(jToggleButton.isSelected()); } }); } return jToggleButton; } protected void showFullScreenWindow(boolean b) { if(window==null){ window = initFullScreenWindow(); } window.setVisible(b); } private Window initFullScreenWindow() { GraphicsEnvironment ge = GraphicsEnvironment.getLocalGraphicsEnvironment(); GraphicsDevice[] gds = ge.getScreenDevices(); GraphicsDevice gd = gds[1]; JWindow window = new JWindow(gd.getDefaultConfiguration()); window.setContentPane(getJFSPanel()); gd.setFullScreenWindow(window); return window; } /** * This method initializes jFSPanel * * @return javax.swing.JPanel */ private JPanel getJFSPanel() { if (jFSPanel == null) { jLabel = new JLabel(); jLabel.setBounds(new Rectangle(18, 19, 500, 66)); jLabel.setText("Hello ! Now, juste open windows explorer and see what happens..."); jFSPanel = new JPanel(); jFSPanel.setLayout(null); jFSPanel.setSize(new Dimension(500, 107)); jFSPanel.add(jLabel, null); } return jFSPanel; } /** * @param args */ public static void main(String[] args) { FullScreenTest me = new FullScreenTest(); me.getJFrame().setVisible(true); } }

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  • multipart file-upload post request from java

    - by Martin
    I'm trying to make a program that uploads a image to a webserver that accepts multipart file-uploads. More specificly i want to make a http POST request to http://iqs.me that sends a file in the variable "pic". I've made a lot of tries but i don't know if i've even been close. The hardest part seems to be to get a HttpURLConnection to make a request of the type POST. The response i get looks like it makes a GET. (And i want to do this without any third party libs) UPDATE: non-working code goes here (no errors but doesn't seem to do a POST): HttpURLConnection conn = null; BufferedReader br = null; DataOutputStream dos = null; DataInputStream inStream = null; InputStream is = null; OutputStream os = null; boolean ret = false; String StrMessage = ""; String exsistingFileName = "myScreenShot.png"; String lineEnd = "\r\n"; String twoHyphens = "--"; String boundary = "*****"; int bytesRead, bytesAvailable, bufferSize; byte[] buffer; int maxBufferSize = 1*1024*1024; String responseFromServer = ""; String urlString = "http://iqs.local.com/index.php"; try{ FileInputStream fileInputStream = new FileInputStream( new File(exsistingFileName) ); URL url = new URL(urlString); conn = (HttpURLConnection) url.openConnection(); conn.setDoInput(true); conn.setDoOutput(true); conn.setRequestMethod("POST"); conn.setUseCaches(false); conn.setRequestProperty("Connection", "Keep-Alive"); conn.setRequestProperty("Content-Type", "multipart/form-data;boundary="+boundary); dos = new DataOutputStream( conn.getOutputStream() ); dos.writeBytes(twoHyphens + boundary + lineEnd); dos.writeBytes("Content-Disposition: form-data; name=\"pic\";" + " filename=\"" + exsistingFileName +"\"" + lineEnd); dos.writeBytes(lineEnd); bytesAvailable = fileInputStream.available(); bufferSize = Math.min(bytesAvailable, maxBufferSize); buffer = new byte[bufferSize]; bytesRead = fileInputStream.read(buffer, 0, bufferSize); while (bytesRead > 0){ dos.write(buffer, 0, bufferSize); bytesAvailable = fileInputStream.available(); bufferSize = Math.min(bytesAvailable, maxBufferSize); bytesRead = fileInputStream.read(buffer, 0, bufferSize); } dos.writeBytes(lineEnd); dos.writeBytes(twoHyphens + boundary + twoHyphens + lineEnd); fileInputStream.close(); dos.flush(); dos.close(); }catch (MalformedURLException ex){ System.out.println("Error:"+ex); }catch (IOException ioe){ System.out.println("Error:"+ioe); } try{ inStream = new DataInputStream ( conn.getInputStream() ); String str; while (( str = inStream.readLine()) != null){ System.out.println(str); } inStream.close(); }catch (IOException ioex){ System.out.println("Error: "+ioex); }

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  • XSLT Select all nodes containing a specific substing

    - by Mike
    I'm trying to write an XPath that will select certain nodes that contain a specific word. In this case the word is, "Lockwood". The correct answer is 3. Both of these paths give me 3. count(//*[contains(./*,'Lockwood')]) count(BusinessLetter/*[contains(../*,'Lockwood')]) But when I try to output the text of each specific node //*[contains(./*,'Lockwood')][1] //*[contains(./*,'Lockwood')][2] //*[contains(./*,'Lockwood')][3] Node 1 ends up containing all the text and nodes 2 and 3 are blank. Can some one please tell me what's happening or what I'm doing wrong. Thanks. <?xml version="1.0" encoding="UTF-8"?> <?xml-stylesheet type="text/xsl" href="XPathFunctions.xsl"?> <BusinessLetter> <Head> <SendDate>November 29, 2005</SendDate> <Recipient> <Name Title="Mr."> <FirstName>Joshua</FirstName> <LastName>Lockwood</LastName> </Name> <Company>Lockwood &amp; Lockwood</Company> <Address> <Street>291 Broadway Ave.</Street> <City>New York</City> <State>NY</State> <Zip>10007</Zip> <Country>United States</Country> </Address> </Recipient> </Head> <Body> <List> <Heading>Along with this letter, I have enclosed the following items:</Heading> <ListItem>two original, execution copies of the Webucator Master Services Agreement</ListItem> <ListItem>two original, execution copies of the Webucator Premier Support for Developers Services Description between Lockwood &amp; Lockwood and Webucator, Inc.</ListItem> </List> <Para>Please sign and return all four original, execution copies to me at your earliest convenience. Upon receipt of the executed copies, we will immediately return a fully executed, original copy of both agreements to you.</Para> <Para>Please send all four original, execution copies to my attention as follows: <Person> <Name> <FirstName>Bill</FirstName> <LastName>Smith</LastName> </Name> <Address> <Company>Webucator, Inc.</Company> <Street>4933 Jamesville Rd.</Street> <City>Jamesville</City> <State>NY</State> <Zip>13078</Zip> <Country>USA</Country> </Address> </Person> </Para> <Para>If you have any questions, feel free to call me at <Phone>800-555-1000 x123</Phone> or e-mail me at <Email>[email protected]</Email>.</Para> </Body> <Foot> <Closing> <Name> <FirstName>Bill</FirstName> <LastName>Smith</LastName> </Name> <JobTitle>VP of Operations</JobTitle> </Closing> </Foot> </BusinessLetter>

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  • Play! Framework 1.2.4 --- C3P0 settings to avoid Communications link failure do to idle time

    - by HelpMeStackOverflowMyOnlyHope
    I'm trying to customize my C3P0 settings to avoid the error shown at the bottom of this post. It was suggested at this url --- http://make-it-open.blogspot.com/2008/12/sql-error-0-sqlstate-08s01.html --- to adjust the settings as follows: In hibernate.cfg.xml, write <property name="c3p0.min_size">5</property> <property name="c3p0.max_size">20</property> <property name="c3p0.timeout">1800</property> <property name="c3p0.max_statements">50</property> Then create "c3p0.properties" in your root classpath folder and write c3p0.testConnectionOnCheckout=true c3p0.acquireRetryDelay=1000 c3p0.acquireRetryAttempts=1 I've tried to make those adjustments following the direction of the Play! Framework documentation, where they say use "db.pool..." as follows: db.pool.timeout=1800 db.pool.maxSize=15 db.pool.minSize=5 db.pool.initialSize=5 db.pool.acquireRetryAttempts=1 db.pool.preferredTestQuery=SELECT 1 db.pool.testConnectionOnCheckout=true db.pool.acquireRetryDelay=1000 db.pool.maxStatements=50 Are those settings not going to work? Should I be trying to set them in a different way? With those settings I still get the error shown below, that is due to to long of a idle time. Complete Stack Trace of Error: 23:00:44,932 WARN ~ SQL Error: 0, SQLState: 08S01 2012-04-13T23:00:44+00:00 app[web.1]: 23:00:44,932 ERROR ~ Communications link failure 2012-04-13T23:00:44+00:00 app[web.1]: 2012-04-13T23:00:44+00:00 app[web.1]: The last packet successfully received from the server was 274,847 milliseconds ago. The last packet sent successfully to the server was 7 milliseconds ago. 2012-04-13T23:00:44+00:00 app[web.1]: 23:00:44,934 ERROR ~ Why the driver complains here? 2012-04-13T23:00:44+00:00 app[web.1]: com.mysql.jdbc.exceptions.jdbc4.MySQLNonTransientConnectionException: No operations allowed after connection closed.Connection was implicitly closed by the driver. 2012-04-13T23:00:44+00:00 app[web.1]: at com.mysql.jdbc.Util.handleNewInstance(Util.java:407) 2012-04-13T23:00:44+00:00 app[web.1]: at com.mysql.jdbc.Util.getInstance(Util.java:382) 2012-04-13T23:00:44+00:00 app[web.1]: at com.mysql.jdbc.SQLError.createSQLException(SQLError.java:1013) 2012-04-13T23:00:44+00:00 app[web.1]: at com.mysql.jdbc.SQLError.createSQLException(SQLError.java:987) 2012-04-13T23:00:44+00:00 app[web.1]: at com.mysql.jdbc.SQLError.createSQLException(SQLError.java:982) 2012-04-13T23:00:44+00:00 app[web.1]: at com.mysql.jdbc.SQLError.createSQLException(SQLError.java:927) 2012-04-13T23:00:44+00:00 app[web.1]: at com.mysql.jdbc.ConnectionImpl.throwConnectionClosedException(ConnectionImpl.java:1213) 2012-04-13T23:00:44+00:00 app[web.1]: at com.mysql.jdbc.ConnectionImpl.getMutex(ConnectionImpl.java:3101) 2012-04-13T23:00:44+00:00 app[web.1]: at com.mysql.jdbc.ConnectionImpl.setAutoCommit(ConnectionImpl.java:4975) 2012-04-13T23:00:44+00:00 app[web.1]: at org.hibernate.jdbc.BorrowedConnectionProxy.invoke(BorrowedConnectionProxy.java:74) 2012-04-13T23:00:44+00:00 app[web.1]: at $Proxy49.setAutoCommit(Unknown Source) 2012-04-13T23:00:44+00:00 app[web.1]: at play.db.jpa.JPAPlugin.closeTx(JPAPlugin.java:368) 2012-04-13T23:00:44+00:00 app[web.1]: at play.db.jpa.JPAPlugin.onInvocationException(JPAPlugin.java:328) 2012-04-13T23:00:44+00:00 app[web.1]: at play.plugins.PluginCollection.onInvocationException(PluginCollection.java:447) 2012-04-13T23:00:44+00:00 app[web.1]: at play.Invoker$Invocation.onException(Invoker.java:240) 2012-04-13T23:00:44+00:00 app[web.1]: at play.jobs.Job.onException(Job.java:124) 2012-04-13T23:00:44+00:00 app[web.1]: at play.jobs.Job.call(Job.java:163) 2012-04-13T23:00:44+00:00 app[web.1]: at play.jobs.Job$1.call(Job.java:66) 2012-04-13T23:00:44+00:00 app[web.1]: at java.util.concurrent.FutureTask$Sync.innerRun(FutureTask.java:334) 2012-04-13T23:00:44+00:00 app[web.1]: at java.util.concurrent.FutureTask.run(FutureTask.java:166) 2012-04-13T23:00:44+00:00 app[web.1]: at java.util.concurrent.ScheduledThreadPoolExecutor$ScheduledFutureTask.access$101(ScheduledThreadPoolExecutor.java:165) 2012-04-13T23:00:44+00:00 app[web.1]: at java.util.concurrent.ScheduledThreadPoolExecutor$ScheduledFutureTask.run(ScheduledThreadPoolExecutor.java:266) 2012-04-13T23:00:44+00:00 app[web.1]: at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1110) 2012-04-13T23:00:44+00:00 app[web.1]: at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:603) 2012-04-13T23:00:44+00:00 app[web.1]: at java.lang.Thread.run(Thread.java:636) 2012-04-13T23:00:44+00:00 app[web.1]: Caused by: com.mysql.jdbc.exceptions.jdbc4.CommunicationsException: Communications link failure

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  • My IDE is showing "undeclared FileNotFoundException must be caught or thrown"

    - by Dan Czarnecki
    I am having the following issue above. I have tried actually putting a try-catch statement into the code as you will see below, but I can't get the compiler to get past that. import java.io.*; public class DirectoryStatistics extends DirectorySize { /* Dan Czarnecki October 24, 2013 Class variables: private File directory A File object that holds the pathname of the directory to look in private long sizeInBytes A variable of type long that holds the size of a file/directory (in bytes) private long fileCount A variable of type long that holds the number of files in a directory Constructors: public DirectoryStatistics(File startingDirectory) throws FileNotFoundException Creates a DirectoryStatistics object, given a pathname (inherited from DirectorySize class), and has 3 instance variables that hold the directory to search in, the size of each file (in bytes), and the number of files within the directory Modification history: October 24, 2013 Original version of class */ private File directory; private long sizeInBytes; private long fileCount; public DirectoryStatistics(File startingDirectory) throws FileNotFoundException { super(startingDirectory); try { if(directory == null) { throw new IllegalArgumentException("null input"); } if(directory.isDirectory() == false) { throw new FileNotFoundException("the following input is not a directory!"); } } catch(IOException ioe) { System.out.println("You have not entered a directory. Please try again."); } } public File getDirectory() { return this.directory; } public long getSizeInBytes() { return this.sizeInBytes; } public long getFileCount() { return this.fileCount; } public long setFileCount(long size) { fileCount = size; return size; } public long setSizeInBytes(long size) { sizeInBytes = size; return size; } public void incrementFileCount() { fileCount = fileCount + 1; } public void addToSizeInBytes(long addend) { sizeInBytes = sizeInBytes + addend; } public String toString() { return "Directory" + this.directory + "Size (in bytes) " + this.sizeInBytes + "Number of files: " + this.fileCount; } public int hashCode() { return this.directory.hashCode(); } public boolean equals(DirectoryStatistics other) { return this.equals(other); } } import java.io.*; import java.util.*; public class DirectorySize extends DirectoryProcessor { /* Dan Czarnecki October 17, 2013 Class variables: private Vector<Long> directorySizeList Variable of type Vector<Long> that holds the total file size of files in that directory as well as files within folders of that directory private Vector<File> currentFile Variable of type Vector<File> that holds the parent directory Constructors: public DirectorySize(File startingDirectory) throws FileNotFoundException Creates a DirectorySize object, takes in a pathname (inherited from DirectoryProcessor class, and has a single vector of a DirectoryStatistics object to hold the files and folders within a directory Modification History October 17, 2013 Original version of class Implemented run() and processFile() methods */ private Vector<DirectoryStatistics> directory; /* private Vector<Long> directorySizeList; private Vector<File> currentFile; */ public DirectorySize(File startingDirectory) throws FileNotFoundException { super(startingDirectory); directory = new Vector<DirectoryStatistics>(); } public void processFile(File file) { DirectoryStatistics parent; int index; File parentFile; System.out.println(file.getName()); System.out.println(file.getParent()); parentFile = file.getParentFile(); parent = new DirectoryStatistics(parentFile); System.out.println(parent); parent.equals(parent); index = directory.indexOf(parent); if(index == 0) { directory.elementAt(index).addToSizeInBytes(file.length()); directory.elementAt(index).incrementFileCount(); } if(index < 0) { directory.addElement(parent); directory.lastElement().setSizeInBytes(file.length()); directory.lastElement().incrementFileCount(); } Could someone tell me why I'm getting this issue?

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  • Unnecessary Java context switches

    - by Paul Morrison
    I have a network of Java Threads (Flow-Based Programming) communicating via fixed-capacity channels - running under WindowsXP. What we expected, based on our experience with "green" threads (non-preemptive), would be that threads would switch context less often (thus reducing CPU time) if the channels were made bigger. However, we found that increasing channel size does not make any difference to the run time. What seems to be happening is that Java decides to switch threads even though channels aren't full or empty (i.e. even though a thread doesn't have to suspend), which costs CPU time for no apparent advantage. Also changing Thread priorities doesn't make any observable difference. My question is whether there is some way of persuading Java not to make unnecessary context switches, but hold off switching until it is really necessary to switch threads - is there some way of changing Java's dispatching logic? Or is it reacting to something I didn't pay attention to?! Or are there other asynchronism mechanisms, e.g. Thread factories, Runnable(s), maybe even daemons (!). The answer appears to be non-obvious, as so far none of my correspondents has come up with an answer (including most recently two CS profs). Or maybe I'm missing something that's so obvious that people can't imagine my not knowing it... I've added the send and receive code here - not very elegant, but it seems to work...;-) In case you are wondering, I thought the goLock logic in 'send' might be causing the problem, but removing it temporarily didn't make any difference. I have added the code for send and receive... public synchronized Packet receive() { if (isDrained()) { return null; } while (isEmpty()) { try { wait(); } catch (InterruptedException e) { close(); return null; } if (isDrained()) { return null; } } if (isDrained()) { return null; } if (isFull()) { notifyAll(); // notify other components waiting to send } Packet packet = array[receivePtr]; array[receivePtr] = null; receivePtr = (receivePtr + 1) % array.length; //notifyAll(); // only needed if it was full usedSlots--; packet.setOwner(receiver); if (null == packet.getContent()) { traceFuncs("Received null packet"); } else { traceFuncs("Received: " + packet.toString()); } return packet; } synchronized boolean send(final Packet packet, final OutputPort op) { sender = op.sender; if (isClosed()) { return false; } while (isFull()) { try { wait(); } catch (InterruptedException e) { indicateOneSenderClosed(); return false; } sender = op.sender; } if (isClosed()) { return false; } try { receiver.goLock.lockInterruptibly(); } catch (InterruptedException ex) { return false; } try { packet.clearOwner(); array[sendPtr] = packet; sendPtr = (sendPtr + 1) % array.length; usedSlots++; // move this to here if (receiver.getStatus() == StatusValues.DORMANT || receiver.getStatus() == StatusValues.NOT_STARTED) { receiver.activate(); // start or wake up if necessary } else { notifyAll(); // notify receiver // other components waiting to send to this connection may also get // notified, // but this is handled by while statement } sender = null; Component.network.active = true; } finally { receiver.goLock.unlock(); } return true; }

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  • Facelet selectOneMenu with POJOs and converter problem

    - by c0d3x
    Hi, I want to have a facelet page with a formular and a dropdown menu. With the dropdown menu the user shoul select a POJO of the type Lieferant: public class Lieferant extends AbstractPersistentWarenwirtschaftsObject { private String firma; public Lieferant(WarenwirtschaftDatabaseLayer database, String firma) { this(database, null, firma); } public Lieferant(WarenwirtschaftDatabaseLayer database, Long primaryKey, String firma) { super(database, primaryKey); this.firma = firma; } public String getFirma() { return firma; } @Override public String toString() { return getFirma(); } @Override public int hashCode() { final int prime = 31; int result = 1; result = prime * result + ((firma == null) ? 0 : firma.hashCode()); return result; } @Override public boolean equals(Object obj) { if (this == obj) return true; if (obj == null) return false; if (getClass() != obj.getClass()) return false; Lieferant other = (Lieferant) obj; if (firma == null) { if (other.firma != null) return false; } else if (!firma.equals(other.firma)) return false; return true; } } Here is the facelet code that I wrote: <h:selectOneMenu> tag. This tag should display a list of POJOs (not beans) of the type Lieferant. Here is the facelet code: <h:selectOneMenu id="lieferant" value="#{lieferantenBestellungBackingBean.lieferant}"> <f:selectItems var="lieferant" value="#{lieferantenBackingBean.lieferanten}" itemLabel="#{lieferant.firma}" itemValue="#{lieferant.primaryKey}" /> <f:converter converterId="LieferantConverter" /> </h:selectOneMenu> Here is the refenrenced managed backing bean @ManagedBean @RequestScoped public class LieferantenBackingBean extends AbstractWarenwirtschaftsBackingBean { private List<Lieferant> lieferanten; public List<Lieferant> getLieferanten() { if (lieferanten == null) { lieferanten = getApplication().getLieferanten(); } return lieferanten; } } As far as I know, I need a custom converter, to swap beetween POJO and String representations of the Lieferant objects. Here is what the converter looks like: @FacesConverter(value="LieferantConverter") public class LieferantConverter implements Converter { @Override public Object getAsObject(FacesContext context, UIComponent component, String value) { long primaryKey = Long.parseLong(value); WarenwirtschaftApplicationLayer application = WarenwirtschaftApplication.getInstance(); Lieferant lieferant = application.getLieferant(primaryKey); return lieferant; } @Override public String getAsString(FacesContext context, UIComponent component, Object value) { return value.toString(); } } The page loads without any error. When I fill out the formular and submit it, there is an error message displayed on the page: Bestellung:lieferantenBestellungForm:lieferant: Validierungsfehler: Wert ist keine gültige Auswahl translated: validation error: value is not a valid selection Unfortunaltely it does not say which value it is talking about. The converter seems to work correctly. I found this similar question from stackoverflow and this article about selectOneMenu and converters, but I was not able to find the problem in my code. Why is List<SelectItem> used in the example from the second link. Gives the same error for me. Any help would be appreciated. Thanks in advance.

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  • WPF BackgroundWorker Execution

    - by Sanju
    Hi All, I've been programming C# for a while now (I'm a Computer Science major), and have never had to implement threading. I am currently building an application for a client that requires threading for a series of operations. Due to the nature of the client/provider agreement, I cannot release the source I am working with. The code that I have posted is in a general form. Pretty much the basic idea of what I am implementing, excluding the content specific source. The first Snippet demonstrates my basic structure, The Progress class is a custom progress window that is displayed as a dialog to prevent user UI interaction. I am currently using the code to complete database calls based on a collection of objects in another area of the application code. For example, I have a collection of "Objects" of one of my custom classes, that I perform these database calls on or on behalf of. My current set up works just fine when I call the "GeneralizedFunction" one and only one time. What I need to do is call this function once for every object in the collection. I was attempting to use a foreach loop to iterate through the collection, then I tried a for loop. For both loops, the result was the same. The Async operation performs exactly as desired for the first item in the collection. This, however, is the only one it works for. For each subsequent item, the progress box (my custom window) displays and immediately closes. In terms of the database calls, the calls for the first item in the collection are the only ones that successfully complete. All others aren't attempted. I've tried everything that I know and don't know to do, but I just cannot seem to get it to work. How can I get this to work for my entire collection? Any and all help is very greatly appreciated. Progress progress; BackgroundWorker worker; // Cancel the current process private void CancelProcess(object sender, EventArgs e) { worker.CancelAsync(); } // The main process ... "Generalized" private void GeneralizedFunction() { progress = new Progress(); progress.Cancel += CancelProcess; progress.Owner = this; Dispatcher pDispatcher = progress.Dispatcher; worker = new BackgroundWorker(); worker.WorkerSupportsCancellation = true; object[] workArgs = { arg1, arg2, arg3}; worker.DoWork += delegate(object s, DoWorkEventArgs args) { /* All main logic here */ foreach(Class ClassObject in ClassObjectCollection) { //Some more logic here UpdateProgressDelegate update = new UpdateProgressDelegate(updateProgress); pDispatcher.BeginInvoke(update, arg1,arg2,arg3); Thread.Sleep(1000); } }; worker.RunWorkerCompleted += delegate(object s, RunWorkerCompletedEventArgs args) { progress.Close(); }; worker.RunWorkerAsync(workArgs); progress.ShowDialog(); } public delegate void UpdateProgressDelegate(arg1,arg2,arg3); private void updateProgress(arg1,arg2,arg3) { //Update progress }

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  • Arduino crashes when sending bytes from Java [on hold]

    - by francisaugusto
    I used the sample program from the arduino website in order to send and receive data via serial to my Arduino one. However, for some reason, even when I try to send only one byte, the Arduino crashes after a while. It doesn't happen if I send the chars manually via the IDE's own serial monitor. I wrote the following method to output the character to Arduino: public synchronized void serialWrite(char sendIt){ try { output.write((byte)'0'); output.flush(); for (int j=0;j<1000000000;j++){ } }catch (Exception e){System.out.println("Not connected...");} notify(); } What I try above is to send just one character when the method is called. I send just a '0' char for testing. After manually calling the method two or three times, Arduino crashes. Is there anything I should be looking into? The Arduino code: #include <SoftwareSerial.h> int buttonState=0; int lastButtonState=0; int buttonPushCounter=0; long previousMillis=0; long interval=250; int ledState=LOW; int ledState2=LOW; int ledState3=LOW; long timeElapsed=0; SoftwareSerial portOne(10,11); void setup(){ pinMode(3,OUTPUT); pinMode(4,OUTPUT); pinMode(5,OUTPUT); pinMode(2,INPUT); Serial.begin(9600); portOne.begin(9600); } boolean turnoff; void loop(){ if(portOne.overflow()){ Serial.println("There's an overflow here!"); } buttonState= digitalRead(2); if(buttonState!=lastButtonState){ if (buttonState==HIGH){ buttonPushCounter++; } } lastButtonState=buttonState; if (turnoff){ unsigned long currentMillis=millis(); if (currentMillis-previousMillis>0 && currentMillis-previousMillis<interval){ ledState=HIGH; ledState2=LOW; ledState3=LOW; }else if (currentMillis-previousMillis>interval && currentMillis-previousMillis<interval*2){ ledState=LOW; ledState2=LOW; ledState3=HIGH; }else if (currentMillis-previousMillis>interval*2 && currentMillis-previousMillis<interval*3){ ledState=LOW; ledState2=HIGH; ledState3=LOW; }else if (currentMillis-previousMillis>interval*3){ previousMillis=currentMillis; } digitalWrite(3,ledState); digitalWrite(4,ledState2); digitalWrite(5,ledState3); }else{ digitalWrite(3,LOW); digitalWrite(4,LOW); digitalWrite(5,LOW); } if (buttonPushCounter==1){ Serial.print("Button pressed!\n"); turnoff=!turnoff; buttonPushCounter=0; } noInterrupts(); char ch=Serial.read(); delay(1); if(ch=='0'){ Serial.println("Changed by serial"+turnoff); Serial.println(ch); turnoff=!turnoff; } interrupts(); }

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  • easiest and best way to make a server queue java

    - by houlahan
    i have a server at the moment which makes a new thread for every user connected but after about 6 people are on the server for more than 15 mins it tends to flop and give me java heap out of memory error i have 1 thread that checks with a mysql database every 30 seconds to see if any of the users currently logged on have any new messages. what would be the easiest way to implement a server queue? this is the my main method for my server: public class Server { public static int MaxUsers = 1000; //public static PrintStream[] sessions = new PrintStream[MaxUsers]; public static ObjectOutputStream[] sessions = new ObjectOutputStream[MaxUsers]; public static ObjectInputStream[] ois = new ObjectInputStream[MaxUsers]; private static int port = 6283; public static Connection conn; static Toolkit toolkit; static Timer timer; public static void main(String[] args) { try { conn = (Connection) Mysql.getConnection(); } catch (Exception ex) { Logger.getLogger(Server.class.getName()).log(Level.SEVERE, null, ex); } System.out.println("****************************************************"); System.out.println("* *"); System.out.println("* Cloud Server *"); System.out.println("* ©2010 *"); System.out.println("* *"); System.out.println("* Luke Houlahan *"); System.out.println("* *"); System.out.println("* Server Online *"); System.out.println("* Listening On Port " + port + " *"); System.out.println("* *"); System.out.println("****************************************************"); System.out.println(""); mailChecker(); try { int i; ServerSocket s = new ServerSocket(port); for (i = 0; i < MaxUsers; ++i) { sessions[i] = null; } while (true) { try { Socket incoming = s.accept(); boolean found = false; int numusers = 0; int usernum = -1; synchronized (sessions) { for (i = 0; i < MaxUsers; ++i) { if (sessions[i] == null) { if (!found) { sessions[i] = new ObjectOutputStream(incoming.getOutputStream()); ois[i]= new ObjectInputStream(incoming.getInputStream()); new SocketHandler(incoming, i).start(); found = true; usernum = i; } } else { numusers++; } } if (!found) { ObjectOutputStream temp = new ObjectOutputStream(incoming.getOutputStream()); Person tempperson = new Person(); tempperson.setFlagField(100); temp.writeObject(tempperson); temp.flush(); temp = null; tempperson = null; incoming.close(); } else { } } } catch (IOException ex) { System.out.println(1); Logger.getLogger(Server.class.getName()).log(Level.SEVERE, null, ex); } } } catch (IOException ex) { System.out.println(2); Logger.getLogger(Server.class.getName()).log(Level.SEVERE, null, ex); } } public static void mailChecker() { toolkit = Toolkit.getDefaultToolkit(); timer = new Timer(); timer.schedule(new mailCheck(), 0, 10 * 1000); } }

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  • multipart file-upload post request from java

    - by Martin
    I'm trying to make a program that uploads a image to a webserver that accepts multipart file-uploads. More specificly i want to make a http POST request to http://iqs.me that sends a file in the variable "pic". I've made a lot of tries but i don't know if i've even been close. The hardest part seems to be to get a HttpURLConnection to make a request of the type POST. The response i get looks like it makes a GET. (And i want to do this without any third party libs) UPDATE: non-working code goes here (no errors but doesn't seem to do a POST): HttpURLConnection conn = null; BufferedReader br = null; DataOutputStream dos = null; DataInputStream inStream = null; InputStream is = null; OutputStream os = null; boolean ret = false; String StrMessage = ""; String exsistingFileName = "myScreenShot.png"; String lineEnd = "\r\n"; String twoHyphens = "--"; String boundary = "*****"; int bytesRead, bytesAvailable, bufferSize; byte[] buffer; int maxBufferSize = 1*1024*1024; String responseFromServer = ""; String urlString = "http://iqs.local.com/index.php"; try{ FileInputStream fileInputStream = new FileInputStream( new File(exsistingFileName) ); URL url = new URL(urlString); conn = (HttpURLConnection) url.openConnection(); conn.setDoInput(true); conn.setDoOutput(true); conn.setRequestMethod("POST"); conn.setUseCaches(false); conn.setRequestProperty("Connection", "Keep-Alive"); conn.setRequestProperty("Content-Type", "multipart/form-data;boundary="+boundary); dos = new DataOutputStream( conn.getOutputStream() ); dos.writeBytes(twoHyphens + boundary + lineEnd); dos.writeBytes("Content-Disposition: form-data; name=\"pic\";" + " filename=\"" + exsistingFileName +"\"" + lineEnd); dos.writeBytes(lineEnd); bytesAvailable = fileInputStream.available(); bufferSize = Math.min(bytesAvailable, maxBufferSize); buffer = new byte[bufferSize]; bytesRead = fileInputStream.read(buffer, 0, bufferSize); while (bytesRead > 0){ dos.write(buffer, 0, bufferSize); bytesAvailable = fileInputStream.available(); bufferSize = Math.min(bytesAvailable, maxBufferSize); bytesRead = fileInputStream.read(buffer, 0, bufferSize); } dos.writeBytes(lineEnd); dos.writeBytes(twoHyphens + boundary + twoHyphens + lineEnd); fileInputStream.close(); dos.flush(); dos.close(); }catch (MalformedURLException ex){ System.out.println("Error:"+ex); }catch (IOException ioe){ System.out.println("Error:"+ioe); } try{ inStream = new DataInputStream ( conn.getInputStream() ); String str; while (( str = inStream.readLine()) != null){ System.out.println(str); } inStream.close(); }catch (IOException ioex){ System.out.println("Error: "+ioex); }

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  • How do I launch a WPF app from command.com. I'm getting a FontCache error.

    - by jttraino
    I know this is not ideal, but my constraint is that I have a legacy application written in Clipper. I want to launch a new, WinForms/WPF application from inside the application (to ease transition). This legacy application written in Clipper launches using: SwpRunCmd("C:\MyApp\MyBat.bat",0) The batch file contains something like this command: C:\PROGRA~1\INTERN~1\iexplore "http://QASVR/MyApp/AppWin/MyCompany.MyApp.AppWin.application#MyCompany.MyApp.AppWin.application" It is launching a WinForms/WPF app that is we deploy via ClickOnce. Everything has been going well until we introduced WPF into the application. We were able to easily launch from the legacy application. Since we have introduced WPF, however, we have the following behavior. If we launch via the Clipper application first, we get an exception when launching the application. The error text is: The type initializer for 'System.Windows.FrameworkElement' threw an exception. at System.Windows.FrameworkElement..ctor() at System.Windows.Controls.Panel..ctor() at System.Windows.Controls.DockPanel..ctor() at System.Windows.Forms.Integration.AvalonAdapter..ctor(ElementHost hostControl) at System.Windows.Forms.Integration.ElementHost..ctor() at MyCompany.MyApp.AppWin.Main.InitializeComponent() at MyCompany.MyApp.AppWin.Main..ctor(String[] args) at MyCompany.MyApp.AppWin.Program.Main(String[] args) The type initializer for 'System.Windows.Documents.TextElement' threw an exception. at System.Windows.FrameworkElement..cctor() The type initializer for 'System.Windows.Media.FontFamily' threw an exception. at System.Windows.Media.FontFamily..ctor(String familyName) at System.Windows.SystemFonts.get_MessageFontFamily() at System.Windows.Documents.TextElement..cctor() The type initializer for 'MS.Internal.FontCache.Util' threw an exception. at MS.Internal.FontCache.Util.get_WindowsFontsUriObject() at System.Windows.Media.FontFamily.PreCreateDefaultFamilyCollection() at System.Windows.Media.FontFamily..cctor() Invalid URI: The format of the URI could not be determined. at System.Uri.CreateThis(String uri, Boolean dontEscape, UriKind uriKind) at System.Uri..ctor(String uriString, UriKind uriKind) at MS.Internal.FontCache.Util..cctor() If we launch the application via the URL (in IE) or via the icon on the desktop first, we do not get the exception and application launches as expected. The neat thing is that whatever we launch with first determines whether the app will launch at all. So, if we launch with legacy first, it breaks right away and we can't get the app to run even if we launch with the otherwise successful URL or icon. To get it to work, we have to logout and log back in and start it from the URL or icon. If we first use the URL or the icon, we have no problem launching from the legacy application from that point forward (until we logout and come back in). One other piece of information is that we are able to simulate the problem in the following fashion. If we enter a command prompt using "cmd.exe" and execute a statement to launch from a URL, we are successful. If, however, we enter a command prompt using "command.com" and we execute that same statement, we experience the breaking behavior. We assume it is because the legacy application in Clipper uses the equivalent of command.com to create the shell to spawn the other app. We have tried a bunch of hacks like having command.com run cmd.exe or psexec and then executing, but nothing seems to work. We have some ideas for workarounds (like making the app launch on startup so we force the successful launch from a URL, making all subsequent launches successful), but they all are sub-optimal even though we have a great deal of control over our workstations. To reduce the chance that this is related to permissions, we have given the launching account administrative rights (as well as non-administrative rights in case that made a difference). Any ideas would be greatly-appreciate. Like I said, we have some work arounds, but I would love to avoid them. Thanks!

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  • Languages and VMs: Features that are hard to optimize and why

    - by mrjoltcola
    I'm doing a survey of features in preparation for a research project. Name a mainstream language or language feature that is hard to optimize, and why the feature is or isn't worth the price paid, or instead, just debunk my theories below with anecdotal evidence. Before anyone flags this as subjective, I am asking for specific examples of languages or features, and ideas for optimization of these features, or important features that I haven't considered. Also, any references to implementations that prove my theories right or wrong. Top on my list of hard to optimize features and my theories (some of my theories are untested and are based on thought experiments): 1) Runtime method overloading (aka multi-method dispatch or signature based dispatch). Is it hard to optimize when combined with features that allow runtime recompilation or method addition. Or is it just hard, anyway? Call site caching is a common optimization for many runtime systems, but multi-methods add additional complexity as well as making it less practical to inline methods. 2) Type morphing / variants (aka value based typing as opposed to variable based) Traditional optimizations simply cannot be applied when you don't know if the type of someting can change in a basic block. Combined with multi-methods, inlining must be done carefully if at all, and probably only for a given threshold of size of the callee. ie. it is easy to consider inlining simple property fetches (getters / setters) but inlining complex methods may result in code bloat. The other issue is I cannot just assign a variant to a register and JIT it to the native instructions because I have to carry around the type info, or every variable needs 2 registers instead of 1. On IA-32 this is inconvenient, even if improved with x64's extra registers. This is probably my favorite feature of dynamic languages, as it simplifies so many things from the programmer's perspective. 3) First class continuations - There are multiple ways to implement them, and I have done so in both of the most common approaches, one being stack copying and the other as implementing the runtime to use continuation passing style, cactus stacks, copy-on-write stack frames, and garbage collection. First class continuations have resource management issues, ie. we must save everything, in case the continuation is resumed, and I'm not aware if any languages support leaving a continuation with "intent" (ie. "I am not coming back here, so you may discard this copy of the world"). Having programmed in the threading model and the contination model, I know both can accomplish the same thing, but continuations' elegance imposes considerable complexity on the runtime and also may affect cache efficienty (locality of stack changes more with use of continuations and co-routines). The other issue is they just don't map to hardware. Optimizing continuations is optimizing for the less-common case, and as we know, the common case should be fast, and the less-common cases should be correct. 4) Pointer arithmetic and ability to mask pointers (storing in integers, etc.) Had to throw this in, but I could actually live without this quite easily. My feelings are that many of the high-level features, particularly in dynamic languages just don't map to hardware. Microprocessor implementations have billions of dollars of research behind the optimizations on the chip, yet the choice of language feature(s) may marginalize many of these features (features like caching, aliasing top of stack to register, instruction parallelism, return address buffers, loop buffers and branch prediction). Macro-applications of micro-features don't necessarily pan out like some developers like to think, and implementing many languages in a VM ends up mapping native ops into function calls (ie. the more dynamic a language is the more we must lookup/cache at runtime, nothing can be assumed, so our instruction mix is made up of a higher percentage of non-local branching than traditional, statically compiled code) and the only thing we can really JIT well is expression evaluation of non-dynamic types and operations on constant or immediate types. It is my gut feeling that bytecode virtual machines and JIT cores are perhaps not always justified for certain languages because of this. I welcome your answers.

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  • Rails unknown action suddenly everywhere

    - by Joe
    The weird thing is that my app was working perfectly on Sat, and when I check it out on Monday (after doing nothing to it) I kept getting this problem: This behaviour is only happening on my production server. When I try to login or create a new user or do something that interacts with a form I am getting an unknown action error. A simple retrieval of rows does not throw this error however. I don't have all CRUD operations in most of my controllers because it's not necessary - but Rails always looks for the one that doesn't exist - it seams so anyway. If I make a mistake in the form that would normally throw a validation message to the user it will throw this error too, does that mean it has something to do with the model too (I'm not too Rails experienced and didn't know if that would be the case or not)? This is a general error I am getting - I have super_exception_notifier gem installed, so that's what all the extra params are. Processing SessionsController#new (for OMITTED at 2010-04-12 09:11:12) [GET] Rendering template within layouts/application Rendering sessions/new Completed in 3ms (View: 2, DB: 0) | 200 OK [http://OMITTED.com/session/new] Processing SessionsController#show (for OMITTED at 2010-04-12 09:11:14) [GET] ActionController::UnknownAction (No action responded to show. Actions: create, destroy, error_class_status_codes, error_class_status_codes=, error_layout, error_layout=, exception_notifiable_notification_level, exception_notifiable_notification_level=, exception_notifiable_silent_exceptions, exception_notifiable_silent_exceptions=, exception_notifiable_verbose, exception_notifiable_verbose=, http_status_codes, http_status_codes=, and new): dragonfly (0.5.3) lib/dragonfly/middleware.rb:13:in `call' passenger (2.2.9) lib/phusion_passenger/rack/request_handler.rb:92:in `process_request' passenger (2.2.9) lib/phusion_passenger/abstract_request_handler.rb:207:in `main_loop' passenger (2.2.9) lib/phusion_passenger/railz/application_spawner.rb:400:in `start_request_handler' passenger (2.2.9) lib/phusion_passenger/railz/application_spawner.rb:351:in `handle_spawn_application' passenger (2.2.9) lib/phusion_passenger/utils.rb:184:in `safe_fork' passenger (2.2.9) lib/phusion_passenger/railz/application_spawner.rb:349:in `handle_spawn_application' passenger (2.2.9) lib/phusion_passenger/abstract_server.rb:352:in `__send__' passenger (2.2.9) lib/phusion_passenger/abstract_server.rb:352:in `main_loop' passenger (2.2.9) lib/phusion_passenger/abstract_server.rb:196:in `start_synchronously' passenger (2.2.9) lib/phusion_passenger/abstract_server.rb:163:in `start' passenger (2.2.9) lib/phusion_passenger/railz/application_spawner.rb:209:in `start' passenger (2.2.9) lib/phusion_passenger/spawn_manager.rb:262:in `spawn_rails_application' passenger (2.2.9) lib/phusion_passenger/abstract_server_collection.rb:126:in `lookup_or_add' passenger (2.2.9) lib/phusion_passenger/spawn_manager.rb:256:in `spawn_rails_application' passenger (2.2.9) lib/phusion_passenger/abstract_server_collection.rb:80:in `synchronize' passenger (2.2.9) lib/phusion_passenger/abstract_server_collection.rb:79:in `synchronize' passenger (2.2.9) lib/phusion_passenger/spawn_manager.rb:255:in `spawn_rails_application' passenger (2.2.9) lib/phusion_passenger/spawn_manager.rb:154:in `spawn_application' passenger (2.2.9) lib/phusion_passenger/spawn_manager.rb:287:in `handle_spawn_application' passenger (2.2.9) lib/phusion_passenger/abstract_server.rb:352:in `__send__' passenger (2.2.9) lib/phusion_passenger/abstract_server.rb:352:in `main_loop' passenger (2.2.9) lib/phusion_passenger/abstract_server.rb:196:in `start_synchronously' This is what one of my forms looks like (nothing special) <% form_tag session_path do -%> <p><%= label_tag 'Username' %><br /> <%= text_field_tag 'login', @login %></p> <p><%= label_tag 'password' %><br/> <%= password_field_tag 'password', nil %></p> <p><%= label_tag 'remember_me', 'Remember me' %> <%= check_box_tag 'remember_me', '1', @remember_me %></p> <p><%= submit_tag 'Log in' %></p> <% end -%> It looks like dragonfly is the culprit doesn't it, here's the section from the gem files it says is being naughty: module Dragonfly class Middleware def initialize(app, dragonfly_app_name) @app = app @dragonfly_app_name = dragonfly_app_name end def call(env) response = endpoint.call(env) if response[0] == 404 13 -->> @app.call(env) else response end end I don't know what goes on behind the scenes here so I probably haven't been looking in the right place to fix this issue. Like I said it only throws this in a production environment, which guess is what the 'env' variable is referencing. Thank you for your time! I've spent nearly my whole day trying to figure this out! :(

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  • Add objects to Arraylist inside loop and get a list of them outside loops

    - by AgusDG
    Im already done with a method to do a shot on a board (bidimensional array). THe shot goes from the bottom to the top, and depending of the direction, it do bounces on the walls to get to the top. The thing is that I did the method to represent the trayectory with an 'x'. Now, I want to add the coordinates x and y of each position of the shot (b [x][y]) to and Arraylist of Objects Position. public Position(int row,int col) { this.row = row; this.col = col; } The thing is that the method uses a for loop and inside if loops, and I'll need to create the objects inside, and get them outside. I did that : public static ArrayList<Position> showTrayectory (char [][] b , int shotDirection, char bubble){ int row = 0, col = 0; ArrayList<Position> aListPos = new ArrayList<Position>(); Position positionsOfShot = new Position(row,col); START = ((RIGHT_WALL)/2) + shotDirection; boolean shotRight = false; if(shotDirection < 0) shotRight = false; else if(shotDirection > 0) shotRight = true; for(int y = BOTTOM,x = START ;y >= 0;y--) { if(!isOut(y,x) && !emptyCell(y,x)) break; if(x <= LEFT_WALL) shotRight = true; if(x >= RIGHT_WALL) shotRight = false; if(!isOut(y,x) && shotRight == true) { positionsOfShot = new Position(y,x); aListPos.add(positionsOfShot); b[y][x] = SHOT; ++x; } if(!isOut(y,x) && shotRight == false){ positionsOfShot = new Position(y,x); aListPos.add(positionsOfShot); b[y][x] = SHOT; --x; } } // The nested for loops below are for showing the positions // But I dont need it that way // I must get the trayectory from an ArrayList and print it from there for(int y=0;y < b.length;y++){ System.out.println(); for(int x=0;x < b[y].length;x++){ System.out.print(" "+b [y][x]+" "); } } System.out.println("\nTrayectory of the shot ["+shotDirection+"]"); System.out.println("Next bubble ["+bubble+"]"); for( Position ii : aListPos){ System.out.println("(" + positionsOfShot.getFila() + "," + positionsOfShot.getColumna()+")"); } return aListPos; } The sentence " b[y][x] = SHOT; " is still there, to see the proper trayectory of the shot (its not needed that way), but what I need, is getting the trayectory in an ArrayList, and print the trayectory from there. All that I get is a wrong position, and repeated during the number of positions the shot goes through. I need some help. I suppose the problem is that Im creating and adding Position Objects inside an ArrayList inside loops, but in a wrong way. I will need you to explain me how to do it properly ; ) Thanks in advance. I'll add the output for you see better what is that above haha *************************** y b y b g r b g o y g a a r y o y y r b y g r r o b o y y g b a r y r o a y y o o r r g r - - - x - - - - - - - - - x - - - - - - - - - x - - - - - - - - - x - - - - - - - - - x - - - - - - - - - x - - - - - - - x - - - - - - - x - - - - - - - x - - - Trayectory of the shot [1] Next bubble [y] (5,3) (5,3) (5,3) (5,3) (5,3) (5,3) (5,3) (5,3) (5,3) Action?

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  • Update UI from an event with a thread

    - by tyrone-tudehope
    Im working on a small application to try out an idea that I have. The idea is to periodically update the UI when event of some sort occurs. In the demo I've created, I'm updating a ProgressDialog every 2 seconds for 15 turns. The problem I am having, which I don't quite understand is that when an event is handled, I send a message to the handler which is supposed to update the message in the ProgressDialog. When this happens however, I get an exception which states that I can't update the UI from that thread. The following code appears in my Activity: ProgressDialog diag; String diagMessage = "Started loading..."; final static int MESSAGE_DATA_RECEIVED = 0; final static int MESSAGE_RECEIVE_COMPLETED = 1; final Handler handler = new Handler(){ @Override public void handleMessage(Message msg){ diag.setMessage(diagMessage); switch(msg.what){ case MESSAGE_DATA_RECEIVED: break; case MESSAGE_RECEIVE_COMPLETED: dismissDialog(); killDialog(); break; } } }; Boolean isRunning = false; /** * Called when the activity is first created. */ @Override public void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setupDialog(); if(isRunning){ showDialog(); } setContentView(R.layout.main); } void setupDialog(){ if(diag == null){ diag = new ProgressDialog(ThreadLoading.this); diag.setMessage(diagMessage); } } void showDialog(){ isRunning = true; if(diag != null && !diag.isShowing()){ diag.show(); } } void dismissDialog(){ if(diag != null && diag.isShowing()){ diag.dismiss(); } } void killDialog(){ isRunning = false; } public void onStart(){ super.onStart(); showDialog(); Thread background = new Thread(new Runnable(){ public void run(){ try{ final ThreadRunner tr = new ThreadRunner(); tr.setOnDataReceivedListener(new ThreadRunner.OnDataReceivedListener(){ public void onDataReceived(String message){ diagMessage = message; handler.handleMessage(handler.obtainMessage(MESSAGE_DATA_RECEIVED)); } }); tr.setOnDataDownloadCompletedEventListener(new ThreadRunner.OnDataDownloadCompletedListener(){ public void onDataDownloadCompleted(String message){ diagMessage = message; handler.handleMessage(handler.obtainMessage(MESSAGE_RECEIVE_COMPLETED)); } }); tr.runProcess(); } catch(Throwable t){ throw new RuntimeException(t); } } }); background.start(); } @Override public void onPause(){ super.onPause(); dismissDialog(); } For curiosity sake, here's the code for the ThreadRunner class: public interface OnDataReceivedListener { public void onDataReceived(String message); } public interface OnDataDownloadCompletedListener { public void onDataDownloadCompleted(String message); } private OnDataReceivedListener onDataReceivedEventListener; private OnDataDownloadCompletedListener onDataDownloadCompletedEventListener; int maxLoop = 15; int loopCount = 0; int sleepTime = 2000; public void setOnDataReceivedListener(OnDataReceivedListener onDataReceivedListener){ this.onDataReceivedEventListener = onDataReceivedListener; } public void setOnDataDownloadCompletedEventListener(OnDataDownloadCompletedListener onDataDownloadCompletedListener){ this.onDataDownloadCompletedEventListener = onDataDownloadCompletedListener; } public void runProcess(){ for(loopCount = 0; loopCount < maxLoop; loopCount++){ try{ Thread.sleep(sleepTime); onDataReceivedEventListener.onDataReceived(Integer.toString(loopCount)); } catch(Throwable t){ throw new RuntimeException(t); } } onDataDownloadCompletedEventListener.onDataDownloadCompleted("Download is completed"); } Am I missing something? The logic makes sense to me and it looks like everything should work, I'm using a handler to update the UI like it is recommended. Any help will be appreciated. Thanks, Tyrone P.S. I'm developing for Android 1.5

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  • REST web service keeps first POST parametrs

    - by Diego
    I have a web service in REST, designed with Java and deployed on Tomcat. This is the web service structure: @Path("Personas") public class Personas { @Context private UriInfo context; /** * Creates a new instance of ServiceResource */ public Personas() { } @GET @Produces("text/html") public String consultarEdad (@QueryParam("nombre") String nombre) { ConectorCliente c = new ConectorCliente("root", "cafe.sql", "test"); int edad = c.consultarEdad(nombre); if (edad == Integer.MIN_VALUE) return "-1"; return String.valueOf(edad); } @POST @Produces("text/html") public String insertarPersona(@QueryParam("nombre") String msg, @QueryParam("edad") int edad) { ConectorCliente c = new ConectorCliente("usr", "passwd", "dbname"); c.agregar(msg, edad); return "listo"; } } Where ConectorCliente class is MySQL connector and querying class. So, I had tested this with the @GET actually doing POST work, any user inputed data and information from ma Java FX app and it went direct to webservice's database. However, I changed so the CREATE operation was performed through a webservice responding to an actual POST HTTP request. However, when I run the client and add some info, parameters go OK, but in next time I input different parameters it'll input the same. I run this several times and I can't get the reason of it. This is the clients code: public class WebServicePersonasConsumer { private WebTarget webTarget; private Client client; private static final String BASE_URI = "http://localhost:8080/GetSomeRest/serviciosweb/"; public WebServicePersonasConsumer() { client = javax.ws.rs.client.ClientBuilder.newClient(); webTarget = client.target(BASE_URI).path("Personas"); } public <T> T insertarPersona(Class<T> responseType, String nombre, String edad) throws ClientErrorException { String[] queryParamNames = new String[]{"nombre", "edad"}; String[] queryParamValues = new String[]{nombre, edad}; ; javax.ws.rs.core.Form form = getQueryOrFormParams(queryParamNames, queryParamValues); javax.ws.rs.core.MultivaluedMap<String, String> map = form.asMap(); for (java.util.Map.Entry<String, java.util.List<String>> entry : map.entrySet()) { java.util.List<String> list = entry.getValue(); String[] values = list.toArray(new String[list.size()]); webTarget = webTarget.queryParam(entry.getKey(), (Object[]) values); } return webTarget.request().post(null, responseType); } public <T> T consultarEdad(Class<T> responseType, String nombre) throws ClientErrorException { String[] queryParamNames = new String[]{"nombre"}; String[] queryParamValues = new String[]{nombre}; ; javax.ws.rs.core.Form form = getQueryOrFormParams(queryParamNames, queryParamValues); javax.ws.rs.core.MultivaluedMap<String, String> map = form.asMap(); for (java.util.Map.Entry<String, java.util.List<String>> entry : map.entrySet()) { java.util.List<String> list = entry.getValue(); String[] values = list.toArray(new String[list.size()]); webTarget = webTarget.queryParam(entry.getKey(), (Object[]) values); } return webTarget.request(javax.ws.rs.core.MediaType.TEXT_HTML).get(responseType); } private Form getQueryOrFormParams(String[] paramNames, String[] paramValues) { Form form = new javax.ws.rs.core.Form(); for (int i = 0; i < paramNames.length; i++) { if (paramValues[i] != null) { form = form.param(paramNames[i], paramValues[i]); } } return form; } public void close() { client.close(); } } And this this the code when I perform the operations in a Java FX app: String nombre = nombreTextField.getText(); String edad = edadTextField.getText(); String insertToDatabase = consumidor.insertarPersona(String.class, nombre, edad); So, as parameters are taken from TextFields, is quite odd why second, third, fourth and so on POSTS post the SAME.

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  • Using Spring as a JPA Container

    - by sdoca
    Hi, I found this article which talks about using Spring as a JPA container: http://java.sys-con.com/node/366275 I have never used Spring before this and am trying to make this work and hope someone can help me. In the article it states that you need to annotate a Spring bean with @Transactional and methods/fields with @PersistenceContext in order to provide transaction support and to inject an entity manager. Is there something the defines a bean as a "Spring Bean"? I have a bean class which implements CRUD operations on entities using generics: @Transactional public class GenericCrudServiceBean implements GenericCrudService { @PersistenceContext(unitName="MyData") private EntityManager em; @Override @PersistenceContext public <T> T create(T t) { em.persist(t); return t; } @Override @PersistenceContext public <T> void delete(T t) { t = em.merge(t); em.remove(t); } ... ... ... @Override @PersistenceContext public List<?> findWithNamedQuery(String queryName) { return em.createNamedQuery(queryName).getResultList(); } } Originally I only had this peristence context annotation: @PersistenceContext(unitName="MyData") private EntityManager em; but had a null em when findWithNamedQuery was invoked. Then I annotated the methods as well, but em is still null (no injection?). I was wondering if this had something to do with my bean not being recognized as "Spring". I have done configuration as best I could following the directions in the article including setting the following in my context.xml file: <?xml version="1.0" encoding="UTF-8"?> <beans xmlns:tx="http://www.springframework.org/schema/tx" tx:schemaLocation="http://www.springframework.org/schema/tx http://www.springframework.org/schema/tx/spring-tx-2.0.xsd"> <bean id="entityManagerFactory" class="org.springframework.orm.jpa.LocalContainerEntityManagerFactoryBean"> <property name="persistenceUnitName" value="MyData" /> <property name="dataSource" ref="dataSource" /> <property name="loadTimeWeaver" class="org.springframework.classloading.ReflectiveLoadTimeWeaver" /> <property name="jpaVendorAdapter" ref="jpaAdapter" /> </bean> <bean id="dataSource" class="org.apache.commons.dbcp.BasicDataSource" destroy-method="close"> <property name="driverClassName" value="oracle.jdbc.driver.OracleDriver" /> <property name="url" value="jdbc:oracle:thin:@localhost:1521:MySID" /> <property name="username" value="user" /> <property name="password" value="password" /> <property name="initialSize" value="3" /> <property name="maxActive" value="10" /> </bean> <bean id="jpaAdapter" class="org.springframework.orm.jpa.vendor.EclipseLinkJpaVendorAdapter"> <property name="databasePlatform" value="org.eclipse.persistence.platform.database.OraclePlatform" /> <property name="showSql" value="true" /> </bean> <bean class="org.springframework.ormmjpa.support.PersistenceAnnotationBeanPostProcessor" /> <tx:annotation-driven /> </beans> I guessed that these belonged in the context.xml file because the article never specifically said which file is the "application context" file. If this is wrong, please let me know.

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  • Is there a way to delay compilation of a stored procedure's execution plan?

    - by Ian Henry
    (At first glance this may look like a duplicate of http://stackoverflow.com/questions/421275 or http://stackoverflow.com/questions/414336, but my actual question is a bit different) Alright, this one's had me stumped for a few hours. My example here is ridiculously abstracted, so I doubt it will be possible to recreate locally, but it provides context for my question (Also, I'm running SQL Server 2005). I have a stored procedure with basically two steps, constructing a temp table, populating it with very few rows, and then querying a very large table joining against that temp table. It has multiple parameters, but the most relevant is a datetime "@MinDate." Essentially: create table #smallTable (ID int) insert into #smallTable select (a very small number of rows from some other table) select * from aGiantTable inner join #smallTable on #smallTable.ID = aGiantTable.ID inner join anotherTable on anotherTable.GiantID = aGiantTable.ID where aGiantTable.SomeDateField > @MinDate If I just execute this as a normal query, by declaring @MinDate as a local variable and running that, it produces an optimal execution plan that executes very quickly (first joins on #smallTable and then only considers a very small subset of rows from aGiantTable while doing other operations). It seems to realize that #smallTable is tiny, so it would be efficient to start with it. This is good. However, if I make that a stored procedure with @MinDate as a parameter, it produces a completely inefficient execution plan. (I am recompiling it each time, so it's not a bad cached plan...at least, I sure hope it's not) But here's where it gets weird. If I change the proc to the following: declare @LocalMinDate datetime set @LocalMinDate = @MinDate --where @MinDate is still a parameter create table #smallTable (ID int) insert into #smallTable select (a very small number of rows from some other table) select * from aGiantTable inner join #smallTable on #smallTable.ID = aGiantTable.ID inner join anotherTable on anotherTable.GiantID = aGiantTable.ID where aGiantTable.SomeDateField > @LocalMinDate Then it gives me the efficient plan! So my theory is this: when executing as a plain query (not as a stored procedure), it waits to construct the execution plan for the expensive query until the last minute, so the query optimizer knows that #smallTable is small and uses that information to give the efficient plan. But when executing as a stored procedure, it creates the entire execution plan at once, thus it can't use this bit of information to optimize the plan. But why does using the locally declared variables change this? Why does that delay the creation of the execution plan? Is that actually what's happening? If so, is there a way to force delayed compilation (if that indeed is what's going on here) even when not using local variables in this way? More generally, does anyone have sources on when the execution plan is created for each step of a stored procedure? Googling hasn't provided any helpful information, but I don't think I'm looking for the right thing. Or is my theory just completely unfounded? Edit: Since posting, I've learned of parameter sniffing, and I assume this is what's causing the execution plan to compile prematurely (unless stored procedures indeed compile all at once), so my question remains -- can you force the delay? Or disable the sniffing entirely? The question is academic, since I can force a more efficient plan by replacing the select * from aGiantTable with select * from (select * from aGiantTable where ID in (select ID from #smallTable)) as aGiantTable Or just sucking it up and masking the parameters, but still, this inconsistency has me pretty curious.

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  • Modern alternatives to Java

    - by Ralph
    I have been a Java developer for 14 years and have written an enterprise-level (~500 kloc) Swing application that uses most of the standard library APIs. Recently, I have become disappointed with the progress that the language has made to "modernize" itself, and am looking for an alternative for ongoing development. I have considered moving to the .NET platform, but I have issues with using something the only runs well in Windows (I know about Mono, but that is still far behind Microsoft). I also plan on buying a new Macbook Pro as soon as Apple releases their new rumored Arrandale-based machines and want to develop in an environment that will feel "at home" in Unix/Linux. I have considered using Python or Ruby, but the standard Java library is arguably the largest of any modern language. In JVM-based languages, I looked at Groovy, but am disappointed with its performance. Rumor has it that with the soon-to-be released JDK7, with its InvokeDynamic instruction, this will improve, but I don't know how much. Groovy is also not truly a functional language, although it provides closures and some of the "functional" features on collections. It does not embrace immutability. I have narrowed my search down to two JVM-based alternatives: Scala and Clojure. Each has its strengths and weaknesses. I am looking for opinions. I am not an expert at either of these languages; I have read 2 1/2 books on Scala and am currently reading Stu Halloway's book on Clojure. Scala is strongly statically typed. I know the dynamic language folks claim that static typing is a crutch for not doing unit testing, but it does provide a mechanism for compile-time location of a whole class of errors. Scala is more concise than Java, but not as much as Clojure. Scala's inter-operation with Java seems to be better than Clojure's, in that most Java operations are easier to do in Scala than in Clojure. For example, I can find no way in Clojure to create a non-static initialization block in a class derived from a Java superclass. For example, I like the Apache commons CLI library for command line argument parsing. In Java and Scala, I can create a new Options object and add Option items to it in an initialization block as follows (Java code): final Options options = new Options() { { addOption(new Option("?", "help", false, "Show this usage information"); // other options } }; I can't figure out how to the same thing in Clojure (except by using (doit...)), although that may reflect my lack of knowledge of the language. Clojure's collections are optimized for immutability. They rarely require copy-on-write semantics. I don't know if Scala's immutable collections are implemented using similar algorithms, but Rich Hickey (Clojure's inventor) goes out of his way to explain how that language's data structures are efficient. Clojure was designed from the beginning for concurrency (as was Scala) and with modern multi-core processors, concurrency takes on more importance, but I occasionally need to write simple non-concurrent utilities, and Scala code probably runs a little faster for these applications since it discourages, but does not prohibit, "simple" mutability. One could argue that one-off utilities do not have to be super-fast, but sometimes they do tasks that take hours or days to complete. I know that there is no right answer to this "question", but I thought I would open it up for discussion. Are there other JVM-based languages that can be used for enterprise level development?

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  • this program runs but not correctly numbers arent right, i read numbers from a file and then when i

    - by user320950
    this is what i have to do: write a program that determines the grade dispersal for 100 students You are to read the exam scores into three arrays, one array for each exam. You must then calculate how many students scored A’s (90 or above), B’s (80 or above), C’s (70 or above), D’s (60 or above), and F’s (less than 60). Do this for each exam and write the distribution to the screen. // basic file operations #include <iostream> #include <fstream> using namespace std; int read_file_in_array(double exam[100][3]); double calculate_total(double exam1[], double exam2[], double exam3[]); // function that calcualates grades to see how many 90,80,70,60 //void display_totals(); double exam[100][3]; int main() { double go,go2,go3; double exam[100][3],exam1[100],exam2[100],exam3[100]; go=read_file_in_array(exam); go2=calculate_total(exam1,exam2,exam3); //go3=display_totals(); cout << go,go2,go3; return 0; } /* int display_totals() { int grade_total; grade_total=calculate_total(exam1,exam2,exam3); return 0; } */ double calculate_total(double exam1[],double exam2[],double exam3[]) { int calc_tot,above90=0, above80=0, above70=0, above60=0,i,j, fail=0; double exam[100][3]; calc_tot=read_file_in_array(exam); for(i=0;i<100;i++) { for (j=0; j<3; j++) { exam1[i]=exam[100][0]; exam2[i]=exam[100][1]; exam3[i]=exam[100][2]; if(exam[i][j] <=90 && exam[i][j] >=100) { above90++; { if(exam[i][j] <=80 && exam[i][j] >=89) { above80++; { if(exam[i][j] <=70 && exam[i][j] >=79) { above70++; { if(exam[i][j] <=60 && exam[i][j] >=69) { above60++; { if(exam[i][j] >=59) { fail++; } } } } } } } } } } } return 0; } int read_file_in_array(double exam[100][3]) { ifstream infile; int exam1[100]; int exam2[100]; int exam3[100]; infile.open("grades.txt");// file containing numbers in 3 columns if(infile.fail()) // checks to see if file opended { cout << "error" << endl; } int num, i=0,j=0; while(!infile.eof()) // reads file to end of line { for(i=0;i<100;i++) // array numbers less than 100 { for(j=0;j<3;j++) // while reading get 1st array or element infile >> exam[i][j]; infile >> exam[i][j]; infile >> exam[i][j]; cout << exam[i][j] << endl; { if (! (infile >> exam[i][j]) ) cout << exam[i][j] << endl; } exam[i][j]=exam1[i]; exam[i][j]=exam2[i]; exam[i][j]=exam3[i]; } infile.close(); } return 0; }

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