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• Java Programming Help

  - by user215049

  hi, im a bit confused on this and i dont know how to solve this question that i have been asked, id be grateful if you could assist me on this question, maybe try to tell me what needs to be done, and how. the question is: Write a method called countChars which takes an InputStream as a parameter, reads the stream and returns the number of characters it contains as an int. Any IOExceptions which might occur in the method should be passed back to the method's caller. Note that the method header should show that it is possible that an exception might occur. i attempted this question with the following code: public class countChars { public int countChars(int InputStream) { return InputStream; } } and i get an error message saying : Main.java:26: cannot find symbol symbol : method countChars(java.io.InputStream) location: class Main s1 = "" + countChars(f1); ^ 1 error

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• Generic arrays of parametrized ArrayLists in java?

  - by athena123

  I am new to Java, so I am not aware of the nitty gritties. Why can't I create generic array of parametrized ArrayList? Instead I have to write, ArrayList<String>[] alist = new ArrayList[10]; or I have to create List of ArrayLists. Aren't arrays supposed to be more efficient than ArrayLists? Then why doesn't Java allow it? Also, what is the difference between following two lines. ArrayList<String>[] alist = new ArrayList[10]; ArrayList<String>[] alist = new ArrayList<?>[10];

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• Java: unmark file is read-only

  - by Zombies

  Can I do this on Java? I'm using windows...

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• Java Thread wait() => blocked?

  - by Chris

  According to http://java.sun.com/j2se/1.5.0/docs/api/java/lang/Thread.State.html calling wait() will result a thread to go in BLOCKED state. However this piece of code will result (after being called) in a Thread in WAITING State. class bThread extends Thread { public synchronized void run() { try { wait(); } catch (InterruptedException e) { e.printStackTrace(); } } } Have I got something wrong? Can anybody explain this behaviour to me? Any help would be appreciated!

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• Java Web Application

  - by Mark R

  I am interested in creating a simple web application that will take in user input, convert it to an XML file and send the file to a database. Coding wise I feel I am okay, it is just the general setup and what implementation to use I am a bit unsure of. At the moment I have a JSP page containing a form, the user fills out the form and on submit a get method is sent to a servlet, in the servlet doGet() method the servlet is instantiating a java object and passing it the user inputted data. The java object then writes that data to an XML file and sends it to the database via REST. All I would be interested to know is if this the standard/optimal way of creating such a web application. Any and all feedback is appreciated. Thanks

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• Java Garbage Collection

  - by Codenotguru

  How does garbage collection in Java takes place when two objects are referencing each other?

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• Android Java Eclipse Intent with 2 Projects

  - by user3793685

  Good day! I have 2 Projects in my Eclipse. MainActivity1 and MainActivity2 are the names of the activities. The MainActivity2 is connected to the MainActivity1 via Project in the properties of the MainActivity1. So far, I can call the package of the MainActivity2 from the MainActivity1. Now, below are my problem: I have a button in MainActivity1. What I want to do is after I click on the button in the MainActivity1, it runs the MainActivity2 project and some variables will be passed on to the MainActivity2. I've been searching in google for a while now and I couldn't get the right keyword for it. I've checked some of the questions here in StackOverflow but I'm unable to locate the problem similar to mine with calling and running the MainActivity2 class from the MainActivity1.java I'm a noob in Android Java but have knowledge in other OOP. Any tips will be a great help. Thanks

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• Load a dll library on Java

  - by crimson_king

  I need to load a library written in C on java. I have only dlls and header files. Since I didn't understand how to translate pointers or other derivated types from JNI documentation I tried to use an automating tool for this, gluegen and SWIG, but I couldn't manage on how to use them. I tried to create an interface file for SWIG but it only gives errors. Is there an example on how to load a dll to a java program using ANY tool that works and can generate translated C function and types from .h files ?

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• Comparing Java enum members: == or equals() ?

  - by Bears will eat you

  I know that Java enums are compiled to classes with private constructors and a bunch of public static members. When comparing two members of a given enum, I've always used .equals(), e.g. public useEnums(SomeEnum a) { if(a.equals(SomeEnum.SOME_ENUM_VALUE)) { ... } ... } However, I just came across come code that uses the equals operator == instead: public useEnums2(SomeEnum a) { if(a == SomeEnum.SOME_ENUM_VALUE) { ... } ... } I've been programming in Java for 5+ years, and I thought I understood difference between the two - but I'm still scratching my head at which one is more correct. Which operator is the one I should be using?

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• Getting value in ZK by passing from java

  - by Thida

  I could not take the value that I pass from JAVA code in ZK Spreadsheet (http://www.zkoss.org) file. Here are what I am doing: In java side I call the .zul file String filenames = "test.txt"; htmlPane.setContentsURL("preview.zul?filename=" + filename); In preview.zul file < zk < zscript < ![CDATA[ System.out.println(execution.getArg().get("filename")); ]] < /zscript < zk The the result is NUll Could you help how to write the correct script? Thanks,

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• sending file in java to multiple users

  - by youse

  how to send a file in java to multiple users using UDP?

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• Java Basics: create class object

  - by user1767853

  In C++: class Rectangle { int x, y; public: void set_values (int,int); int area () {return (x*y);} }; int main () { Rectangle rect; rect.set_values (3,4); } In Java: class Rectangle { int x, y; void set_values (int x,int y); int area () {return (x*y);} } public static void main(String[] args) { Rectangle rect=new Rectangle(3,4); } In C++ compiler will create rect object & reserve memory 4 bytes. I want to know How Java is creating object?

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• Android - doInBackground() error in AsyncTask

  - by AimanB

  What my app here basically does is it captures a photo or import from gallery, and when the Upload button is pressed, the image will be uploaded to a localhost server. Before I implemented AsyncTask into the process, it doesn't have any problem uploading whatsoever. Now that I've put AsyncTask, everything went wrong. I don't know which part that I do wrong in this phase. This is what logcat shows when I try to upload an image file: 10-28 17:23:25.989: E/AndroidRuntime(3356): FATAL EXCEPTION: AsyncTask #5 10-28 17:23:25.989: E/AndroidRuntime(3356): java.lang.RuntimeException: An error occured while executing doInBackground() 10-28 17:23:25.989: E/AndroidRuntime(3356): at android.os.AsyncTask$3.done(AsyncTask.java:299) 10-28 17:23:25.989: E/AndroidRuntime(3356): at java.util.concurrent.FutureTask.finishCompletion(FutureTask.java:352) 10-28 17:23:25.989: E/AndroidRuntime(3356): at java.util.concurrent.FutureTask.setException(FutureTask.java:219) 10-28 17:23:25.989: E/AndroidRuntime(3356): at java.util.concurrent.FutureTask.run(FutureTask.java:239) 10-28 17:23:25.989: E/AndroidRuntime(3356): at android.os.AsyncTask$SerialExecutor$1.run(AsyncTask.java:230) 10-28 17:23:25.989: E/AndroidRuntime(3356): at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1080) 10-28 17:23:25.989: E/AndroidRuntime(3356): at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:573) 10-28 17:23:25.989: E/AndroidRuntime(3356): at java.lang.Thread.run(Thread.java:856) 10-28 17:23:25.989: E/AndroidRuntime(3356): Caused by: java.lang.RuntimeException: Can't create handler inside thread that has not called Looper.prepare() 10-28 17:23:25.989: E/AndroidRuntime(3356): at android.os.Handler.<init>(Handler.java:197) 10-28 17:23:25.989: E/AndroidRuntime(3356): at android.os.Handler.<init>(Handler.java:111) 10-28 17:23:25.989: E/AndroidRuntime(3356): at android.widget.Toast$TN.<init>(Toast.java:324) 10-28 17:23:25.989: E/AndroidRuntime(3356): at android.widget.Toast.<init>(Toast.java:91) 10-28 17:23:25.989: E/AndroidRuntime(3356): at android.widget.Toast.makeText(Toast.java:238) 10-28 17:23:25.989: E/AndroidRuntime(3356): at com.aiman.webshopper.UploadImageActivity$1execMultiPostAsync.doInBackground(UploadImageActivity.java:268) 10-28 17:23:25.989: E/AndroidRuntime(3356): at com.aiman.webshopper.UploadImageActivity$1execMultiPostAsync.doInBackground(UploadImageActivity.java:1) 10-28 17:23:25.989: E/AndroidRuntime(3356): at android.os.AsyncTask$2.call(AsyncTask.java:287) 10-28 17:23:25.989: E/AndroidRuntime(3356): at java.util.concurrent.FutureTask.run(FutureTask.java:234) This is my code for the Upload activity: public class UploadImageActivity extends Activity implements OnItemSelectedListener { InputStream inputStream; private ImageView imageView; String the_string_response; private static final int SELECT_PICTURE = 0; private static final int CAMERA_REQUEST = 1888; private static final String SERVER_UPLOAD_URI = "...myserver.php"; @Override protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.activity_upload_image); imageView = (ImageView) findViewById(R.id.imgUpload); } public void capturePhoto(View view) { Intent cameraIntent = new Intent( android.provider.MediaStore.ACTION_IMAGE_CAPTURE); File f = new File(android.os.Environment.getExternalStorageDirectory(), "temp.jpg"); cameraIntent.putExtra(MediaStore.EXTRA_OUTPUT, Uri.fromFile(f)); startActivityForResult(cameraIntent, CAMERA_REQUEST); } public void pickPhoto(View view) { // TODO: launch the photo picker Intent intent = new Intent(); intent.setType("image/*"); intent.setAction(Intent.ACTION_GET_CONTENT); startActivityForResult(Intent.createChooser(intent, "Select Picture"), SELECT_PICTURE); } @Override protected void onActivityResult(int requestCode, int resultCode, Intent data) { super.onActivityResult(requestCode, resultCode, data); if (requestCode == CAMERA_REQUEST && resultCode == RESULT_OK) { File f = new File(Environment.getExternalStorageDirectory() .toString()); for (File temp : f.listFiles()) { if (temp.getName().equals("temp.jpg")) { f = temp; break; } } try { BitmapFactory.Options bitmapOptions = new BitmapFactory.Options(); Bitmap bitmap = BitmapFactory.decodeFile(f.getAbsolutePath(), bitmapOptions); imageView.setImageBitmap(bitmap); String path = android.os.Environment .getExternalStorageDirectory() + File.separator + "Phoenix" + File.separator + "default"; f.delete(); OutputStream outFile = null; File file = new File(path, String.valueOf(System .currentTimeMillis()) + ".jpg"); try { outFile = new FileOutputStream(file); bitmap.compress(Bitmap.CompressFormat.JPEG, 85, outFile); outFile.flush(); outFile.close(); } catch (FileNotFoundException e) { e.printStackTrace(); } catch (IOException e) { e.printStackTrace(); } catch (Exception e) { e.printStackTrace(); } } catch (Exception e) { e.printStackTrace(); } } if (requestCode == SELECT_PICTURE && resultCode == RESULT_OK) { Bitmap bitmap = getPath(data.getData()); imageView.setImageBitmap(bitmap); } } private Bitmap getPath(Uri uri) { String[] projection = { MediaStore.Images.Media.DATA }; Cursor cursor = getContentResolver().query(uri, projection, null, null, null); int column_index = cursor.getColumnIndexOrThrow(projection[0]); cursor.moveToFirst(); String filePath = cursor.getString(column_index); cursor.close(); // Convert file path into bitmap image using below line. Bitmap bitmap = BitmapFactory.decodeFile(filePath); return bitmap; } public void uploadPhoto(View view) { try { executeMultipartPost(); } catch (Exception e) { e.printStackTrace(); } } public void executeMultipartPost() throws Exception { class execMultiPostAsync extends AsyncTask<String, Void, String>{ @Override protected String doInBackground(String... params){ // Choose image here BitmapDrawable drawable = (BitmapDrawable) imageView.getDrawable(); Bitmap bitmap = drawable.getBitmap(); ByteArrayOutputStream stream = new ByteArrayOutputStream(); bitmap.compress(Bitmap.CompressFormat.JPEG, 50, stream); // compress to // which // format // you want. byte[] byte_arr = stream.toByteArray(); String image_str = Base64.encodeBytes(byte_arr); ArrayList<NameValuePair> nameValuePairs = new ArrayList<NameValuePair>(); nameValuePairs.add(new BasicNameValuePair("image", image_str)); try { HttpClient httpclient = new DefaultHttpClient(); /* * HttpPost(parameter): Server URI */ HttpPost httppost = new HttpPost(SERVER_UPLOAD_URI); httppost.setEntity(new UrlEncodedFormEntity(nameValuePairs)); HttpResponse response = httpclient.execute(httppost); the_string_response = convertResponseToString(response); } catch (Exception e) { Toast.makeText(UploadImageActivity.this, "ERROR " + e.getMessage(), Toast.LENGTH_LONG).show(); System.out.println("Error in http connection " + e.toString()); } return the_string_response; } @Override protected void onPostExecute(String result) { super.onPostExecute(result); Toast.makeText(UploadImageActivity.this, "Response " + result, Toast.LENGTH_LONG) .show(); } public String convertResponseToString(HttpResponse response) throws IllegalStateException, IOException { String res = ""; StringBuffer buffer = new StringBuffer(); inputStream = response.getEntity().getContent(); int contentLength = (int) response.getEntity().getContentLength(); // getting // content // lengt Toast.makeText(UploadImageActivity.this, "contentLength : " + contentLength, Toast.LENGTH_LONG).show(); if (contentLength < 0) { } else { byte[] data = new byte[512]; int len = 0; try { while (-1 != (len = inputStream.read(data))) { buffer.append(new String(data, 0, len)); // converting to // string and // appending to // stringbuffer } } catch (IOException e) { e.printStackTrace(); } try { inputStream.close(); // closing the stream } catch (IOException e) { e.printStackTrace(); } res = buffer.toString(); // converting stringbuffer to string Toast.makeText(UploadImageActivity.this, "Result : " + res, Toast.LENGTH_LONG).show(); // System.out.println("Response => " + // EntityUtils.toString(response.getEntity())); } return res; } } execMultiPostAsync exec = new execMultiPostAsync(); exec.execute(); } } Can someone please check if I put the AsyncTask task correctly in this activity? I think I've made a mistake somewhere.

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• ActiveMQ - "Cannot send, channel has already failed" every 2 seconds?

  - by quanta

  ActiveMQ 5.7.0 In the activemq.log, I'm seeing this exception every 2 seconds: 2013-11-05 13:00:52,374 | DEBUG | Transport Connection to: tcp://127.0.0.1:37501 failed: org.apache.activemq.transport.InactivityIOException: Cannot send, channel has already failed: tcp://127.0.0.1:37501 | org.apache.activemq.broker.TransportConnection.Transport | Async Exception Handler org.apache.activemq.transport.InactivityIOException: Cannot send, channel has already failed: tcp://127.0.0.1:37501 at org.apache.activemq.transport.AbstractInactivityMonitor.doOnewaySend(AbstractInactivityMonitor.java:282) at org.apache.activemq.transport.AbstractInactivityMonitor.oneway(AbstractInactivityMonitor.java:271) at org.apache.activemq.transport.TransportFilter.oneway(TransportFilter.java:85) at org.apache.activemq.transport.WireFormatNegotiator.oneway(WireFormatNegotiator.java:104) at org.apache.activemq.transport.MutexTransport.oneway(MutexTransport.java:68) at org.apache.activemq.broker.TransportConnection.dispatch(TransportConnection.java:1312) at org.apache.activemq.broker.TransportConnection.processDispatch(TransportConnection.java:838) at org.apache.activemq.broker.TransportConnection.iterate(TransportConnection.java:873) at org.apache.activemq.thread.PooledTaskRunner.runTask(PooledTaskRunner.java:129) at org.apache.activemq.thread.PooledTaskRunner$1.run(PooledTaskRunner.java:47) at java.util.concurrent.ThreadPoolExecutor$Worker.runTask(ThreadPoolExecutor.java:886) at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:908) at java.lang.Thread.run(Thread.java:662) Due to this keyword InactivityIOException, the first thing comes to my mind is InactivityMonitor, but the strange thing is MaxInactivityDuration=30000: 2013-11-05 13:11:02,672 | DEBUG | Sending: WireFormatInfo { version=9, properties={MaxFrameSize=9223372036854775807, CacheSize=1024, CacheEnabled=true, SizePrefixDisabled=false, MaxInactivityDurationInitalDelay=10000, TcpNoDelayEnabled=true, MaxInactivityDuration=30000, TightEncodingEnabled=true, StackTraceEnabled=true}, magic=[A,c,t,i,v,e,M,Q]} | org.apache.activemq.transport.WireFormatNegotiator | ActiveMQ BrokerService[localhost] Task-2 Moreover, I also didn't see something like this: No message received since last read check for ... or: Channel was inactive for too (30000) long Do a netstat, I see these connections in TIME_WAIT state: tcp 0 0 127.0.0.1:38545 127.0.0.1:61616 TIME_WAIT - tcp 0 0 127.0.0.1:38544 127.0.0.1:61616 TIME_WAIT - tcp 0 0 127.0.0.1:38522 127.0.0.1:61616 TIME_WAIT - Here're the output when running tcpdump: Internet Protocol Version 4, Src: 127.0.0.1 (127.0.0.1), Dst: 127.0.0.1 (127.0.0.1) Version: 4 Header length: 20 bytes Differentiated Services Field: 0x00 (DSCP 0x00: Default; ECN: 0x00: Not-ECT (Not ECN-Capable Transport)) 0000 00.. = Differentiated Services Codepoint: Default (0x00) .... ..00 = Explicit Congestion Notification: Not-ECT (Not ECN-Capable Transport) (0x00) Total Length: 296 Identification: 0x7b6a (31594) Flags: 0x02 (Don't Fragment) 0... .... = Reserved bit: Not set .1.. .... = Don't fragment: Set ..0. .... = More fragments: Not set Fragment offset: 0 Time to live: 64 Protocol: TCP (6) Header checksum: 0xc063 [correct] [Good: True] [Bad: False] Source: 127.0.0.1 (127.0.0.1) Destination: 127.0.0.1 (127.0.0.1) Transmission Control Protocol, Src Port: 61616 (61616), Dst Port: 54669 (54669), Seq: 1, Ack: 2, Len: 244 Source port: 61616 (61616) Destination port: 54669 (54669) [Stream index: 11] Sequence number: 1 (relative sequence number) [Next sequence number: 245 (relative sequence number)] Acknowledgement number: 2 (relative ack number) Header length: 32 bytes Flags: 0x018 (PSH, ACK) 000. .... .... = Reserved: Not set ...0 .... .... = Nonce: Not set .... 0... .... = Congestion Window Reduced (CWR): Not set .... .0.. .... = ECN-Echo: Not set .... ..0. .... = Urgent: Not set .... ...1 .... = Acknowledgement: Set .... .... 1... = Push: Set .... .... .0.. = Reset: Not set .... .... ..0. = Syn: Not set .... .... ...0 = Fin: Not set Window size value: 256 [Calculated window size: 32768] [Window size scaling factor: 128] Checksum: 0xff1c [validation disabled] [Good Checksum: False] [Bad Checksum: False] Options: (12 bytes) No-Operation (NOP) No-Operation (NOP) Timestamps: TSval 2304161892, TSecr 2304161891 Kind: Timestamp (8) Length: 10 Timestamp value: 2304161892 Timestamp echo reply: 2304161891 [SEQ/ACK analysis] [Bytes in flight: 244] Constrained Application Protocol, TID: 240, Length: 244 00.. .... = Version: 0 ..00 .... = Type: Confirmable (0) .... 0000 = Option Count: 0 Code: Unknown (0) Transaction ID: 240 Payload Content-Type: text/plain (default), Length: 240, offset: 4 Line-based text data: text/plain [truncated] \001ActiveMQ\000\000\000\t\001\000\000\000<DE>\000\000\000\t\000\fMaxFrameSize\006\177<FF><FF><FF><FF> <FF><FF><FF>\000\tCacheSize\005\000\000\004\000\000\fCacheEnabled\001\001\000\022SizePrefixDisabled\001\000\000 MaxInactivityDurationInitalDelay\006\ It is very likely a tcp port check. This is what I see when trying telnet from another host: 2013-11-05 16:12:41,071 | DEBUG | Transport Connection to: tcp://10.8.20.9:46775 failed: java.io.EOFException | org.apache.activemq.broker.TransportConnection.Transport | ActiveMQ Transport: tcp:///10.8.20.9:46775@61616 java.io.EOFException at java.io.DataInputStream.readInt(DataInputStream.java:375) at org.apache.activemq.openwire.OpenWireFormat.unmarshal(OpenWireFormat.java:275) at org.apache.activemq.transport.tcp.TcpTransport.readCommand(TcpTransport.java:229) at org.apache.activemq.transport.tcp.TcpTransport.doRun(TcpTransport.java:221) at org.apache.activemq.transport.tcp.TcpTransport.run(TcpTransport.java:204) at java.lang.Thread.run(Thread.java:662) 2013-11-05 16:12:41,071 | DEBUG | Transport Connection to: tcp://10.8.20.9:46775 failed: org.apache.activemq.transport.InactivityIOException: Cannot send, channel has already failed: tcp://10.8.20.9:46775 | org.apache.activemq.broker.TransportConnection.Transport | Async Exception Handler org.apache.activemq.transport.InactivityIOException: Cannot send, channel has already failed: tcp://10.8.20.9:46775 at org.apache.activemq.transport.AbstractInactivityMonitor.doOnewaySend(AbstractInactivityMonitor.java:282) at org.apache.activemq.transport.AbstractInactivityMonitor.oneway(AbstractInactivityMonitor.java:271) at org.apache.activemq.transport.TransportFilter.oneway(TransportFilter.java:85) at org.apache.activemq.transport.WireFormatNegotiator.oneway(WireFormatNegotiator.java:104) at org.apache.activemq.transport.MutexTransport.oneway(MutexTransport.java:68) at org.apache.activemq.broker.TransportConnection.dispatch(TransportConnection.java:1312) at org.apache.activemq.broker.TransportConnection.processDispatch(TransportConnection.java:838) at org.apache.activemq.broker.TransportConnection.iterate(TransportConnection.java:873) at org.apache.activemq.thread.PooledTaskRunner.runTask(PooledTaskRunner.java:129) at org.apache.activemq.thread.PooledTaskRunner$1.run(PooledTaskRunner.java:47) at java.util.concurrent.ThreadPoolExecutor$Worker.runTask(ThreadPoolExecutor.java:886) at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:908) at java.lang.Thread.run(Thread.java:662) 2013-11-05 16:12:41,071 | DEBUG | Unregistering MBean org.apache.activemq:BrokerName=localhost,Type=Connection,ConnectorName=ope nwire,ViewType=address,Name=tcp_//10.8.20.9_46775 | org.apache.activemq.broker.jmx.ManagementContext | ActiveMQ Transport: tcp:/ //10.8.20.9:46775@61616 2013-11-05 16:12:41,073 | DEBUG | Stopping connection: tcp://10.8.20.9:46775 | org.apache.activemq.broker.TransportConnection | ActiveMQ BrokerService[localhost] Task-5 2013-11-05 16:12:41,073 | DEBUG | Stopping transport tcp:///10.8.20.9:46775@61616 | org.apache.activemq.transport.tcp.TcpTranspo rt | ActiveMQ BrokerService[localhost] Task-5 2013-11-05 16:12:41,073 | DEBUG | Initialized TaskRunnerFactory[ActiveMQ Task] using ExecutorService: java.util.concurrent.Threa dPoolExecutor@23cc2a28 | org.apache.activemq.thread.TaskRunnerFactory | ActiveMQ BrokerService[localhost] Task-5 2013-11-05 16:12:41,074 | DEBUG | Closed socket Socket[addr=/10.8.20.9,port=46775,localport=61616] | org.apache.activemq.transpo rt.tcp.TcpTransport | ActiveMQ Task-1 2013-11-05 16:12:41,074 | DEBUG | Forcing shutdown of ExecutorService: java.util.concurrent.ThreadPoolExecutor@23cc2a28 | org.apache.activemq.util.ThreadPoolUtils | ActiveMQ BrokerService[localhost] Task-5 2013-11-05 16:12:41,074 | DEBUG | Stopped transport: tcp://10.8.20.9:46775 | org.apache.activemq.broker.TransportConnection | ActiveMQ BrokerService[localhost] Task-5 2013-11-05 16:12:41,074 | DEBUG | Connection Stopped: tcp://10.8.20.9:46775 | org.apache.activemq.broker.TransportConnection | ActiveMQ BrokerService[localhost] Task-5 2013-11-05 16:12:41,902 | DEBUG | Sending: WireFormatInfo { version=9, properties={MaxFrameSize=9223372036854775807, CacheSize=1024, CacheEnabled=true, SizePrefixDisabled=false, MaxInactivityDurationInitalDelay=10000, TcpNoDelayEnabled=true, MaxInactivityDuration=30000, TightEncodingEnabled=true, StackTraceEnabled=true}, magic=[A,c,t,i,v,e,M,Q]} | org.apache.activemq.transport.WireFormatNegotiator | ActiveMQ BrokerService[localhost] Task-5 So the question is: how can I find out the process that is trying to connect to my ActiveMQ (from localhost) every 2 seconds?

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• Adding Unobtrusive Validation To MVCContrib Fluent Html

  - by srkirkland

  ASP.NET MVC 3 includes a new unobtrusive validation strategy that utilizes HTML5 data-* attributes to decorate form elements.  Using a combination of jQuery validation and an unobtrusive validation adapter script that comes with MVC 3, those attributes are then turned into client side validation rules. A Quick Introduction to Unobtrusive Validation To quickly show how this works in practice, assume you have the following Order.cs class (think Northwind) [If you are familiar with unobtrusive validation in MVC 3 you can skip to the next section]: public class Order : DomainObject { [DataType(DataType.Date)] public virtual DateTime OrderDate { get; set; }   [Required] [StringLength(12)] public virtual string ShipAddress { get; set; }   [Required] public virtual Customer OrderedBy { get; set; } } .csharpcode, .csharpcode pre { font-size: small; color: black; font-family: consolas, "Courier New", courier, monospace; background-color: #ffffff; /*white-space: pre;*/ } .csharpcode pre { margin: 0em; } .csharpcode .rem { color: #008000; } .csharpcode .kwrd { color: #0000ff; } .csharpcode .str { color: #006080; } .csharpcode .op { color: #0000c0; } .csharpcode .preproc { color: #cc6633; } .csharpcode .asp { background-color: #ffff00; } .csharpcode .html { color: #800000; } .csharpcode .attr { color: #ff0000; } .csharpcode .alt { background-color: #f4f4f4; width: 100%; margin: 0em; } .csharpcode .lnum { color: #606060; } Note the System.ComponentModel.DataAnnotations attributes, which provide the validation and metadata information used by ASP.NET MVC 3 to determine how to render out these properties.  Now let’s assume we have a form which can edit this Order class, specifically let’s look at the ShipAddress property: @Html.LabelFor(x => x.Order.ShipAddress) @Html.EditorFor(x => x.Order.ShipAddress) @Html.ValidationMessageFor(x => x.Order.ShipAddress) .csharpcode, .csharpcode pre { font-size: small; color: black; font-family: consolas, "Courier New", courier, monospace; background-color: #ffffff; /*white-space: pre;*/ } .csharpcode pre { margin: 0em; } .csharpcode .rem { color: #008000; } .csharpcode .kwrd { color: #0000ff; } .csharpcode .str { color: #006080; } .csharpcode .op { color: #0000c0; } .csharpcode .preproc { color: #cc6633; } .csharpcode .asp { background-color: #ffff00; } .csharpcode .html { color: #800000; } .csharpcode .attr { color: #ff0000; } .csharpcode .alt { background-color: #f4f4f4; width: 100%; margin: 0em; } .csharpcode .lnum { color: #606060; } Now the Html.EditorFor() method is smart enough to look at the ShipAddress attributes and write out the necessary unobtrusive validation html attributes.  Note we could have used Html.TextBoxFor() or even Html.TextBox() and still retained the same results. If we view source on the input box generated by the Html.EditorFor() call, we get the following: <input type="text" value="Rua do Paço, 67" name="Order.ShipAddress" id="Order_ShipAddress" data-val-required="The ShipAddress field is required." data-val-length-max="12" data-val-length="The field ShipAddress must be a string with a maximum length of 12." data-val="true" class="text-box single-line input-validation-error"> .csharpcode, .csharpcode pre { font-size: small; color: black; font-family: consolas, "Courier New", courier, monospace; background-color: #ffffff; /*white-space: pre;*/ } .csharpcode pre { margin: 0em; } .csharpcode .rem { color: #008000; } .csharpcode .kwrd { color: #0000ff; } .csharpcode .str { color: #006080; } .csharpcode .op { color: #0000c0; } .csharpcode .preproc { color: #cc6633; } .csharpcode .asp { background-color: #ffff00; } .csharpcode .html { color: #800000; } .csharpcode .attr { color: #ff0000; } .csharpcode .alt { background-color: #f4f4f4; width: 100%; margin: 0em; } .csharpcode .lnum { color: #606060; } As you can see, we have data-val-* attributes for both required and length, along with the proper error messages and additional data as necessary (in this case, we have the length-max=”12”). And of course, if we try to submit the form with an invalid value, we get an error on the client: Working with MvcContrib’s Fluent Html The MvcContrib project offers a fluent interface for creating Html elements which I find very expressive and useful, especially when it comes to creating select lists.  Let’s look at a few quick examples: @this.TextBox(x => x.FirstName).Class("required").Label("First Name:") @this.MultiSelect(x => x.UserId).Options(ViewModel.Users) @this.CheckBox("enabled").LabelAfter("Enabled").Title("Click to enable.").Styles(vertical_align => "middle")   @(this.Select("Order.OrderedBy").Options(Model.Customers, x => x.Id, x => x.CompanyName) .Selected(Model.Order.OrderedBy != null ? Model.Order.OrderedBy.Id : "") .FirstOption(null, "--Select A Company--") .HideFirstOptionWhen(Model.Order.OrderedBy != null) .Label("Ordered By:")) .csharpcode, .csharpcode pre { font-size: small; color: black; font-family: consolas, "Courier New", courier, monospace; background-color: #ffffff; /*white-space: pre;*/ } .csharpcode pre { margin: 0em; } .csharpcode .rem { color: #008000; } .csharpcode .kwrd { color: #0000ff; } .csharpcode .str { color: #006080; } .csharpcode .op { color: #0000c0; } .csharpcode .preproc { color: #cc6633; } .csharpcode .asp { background-color: #ffff00; } .csharpcode .html { color: #800000; } .csharpcode .attr { color: #ff0000; } .csharpcode .alt { background-color: #f4f4f4; width: 100%; margin: 0em; } .csharpcode .lnum { color: #606060; } These fluent html helpers create the normal html you would expect, and I think they make life a lot easier and more readable when dealing with complex markup or select list data models (look ma: no anonymous objects for creating class names!). Of course, the problem we have now is that MvcContrib’s fluent html helpers don’t know about ASP.NET MVC 3’s unobtrusive validation attributes and thus don’t take part in client validation on your page.  This is not ideal, so I wrote a quick helper method to extend fluent html with the knowledge of what unobtrusive validation attributes to include when they are rendered. Extending MvcContrib’s Fluent Html Before posting the code, there are just a few things you need to know.  The first is that all Fluent Html elements implement the IElement interface (MvcContrib.FluentHtml.Elements.IElement), and the second is that the base System.Web.Mvc.HtmlHelper has been extended with a method called GetUnobtrusiveValidationAttributes which we can use to determine the necessary attributes to include.  With this knowledge we can make quick work of extending fluent html: public static class FluentHtmlExtensions { public static T IncludeUnobtrusiveValidationAttributes<T>(this T element, HtmlHelper htmlHelper) where T : MvcContrib.FluentHtml.Elements.IElement { IDictionary<string, object> validationAttributes = htmlHelper .GetUnobtrusiveValidationAttributes(element.GetAttr("name"));   foreach (var validationAttribute in validationAttributes) { element.SetAttr(validationAttribute.Key, validationAttribute.Value); }   return element; } } .csharpcode, .csharpcode pre { font-size: small; color: black; font-family: consolas, "Courier New", courier, monospace; background-color: #ffffff; /*white-space: pre;*/ } .csharpcode pre { margin: 0em; } .csharpcode .rem { color: #008000; } .csharpcode .kwrd { color: #0000ff; } .csharpcode .str { color: #006080; } .csharpcode .op { color: #0000c0; } .csharpcode .preproc { color: #cc6633; } .csharpcode .asp { background-color: #ffff00; } .csharpcode .html { color: #800000; } .csharpcode .attr { color: #ff0000; } .csharpcode .alt { background-color: #f4f4f4; width: 100%; margin: 0em; } .csharpcode .lnum { color: #606060; } The code is pretty straight forward – basically we use a passed HtmlHelper to get a list of validation attributes for the current element and then add each of the returned attributes to the element to be rendered. The Extension In Action Now let’s get back to the earlier ShipAddress example and see what we’ve accomplished.  First we will use a fluent html helper to render out the ship address text input (this is the ‘before’ case): @this.TextBox("Order.ShipAddress").Label("Ship Address:").Class("class-name") .csharpcode, .csharpcode pre { font-size: small; color: black; font-family: consolas, "Courier New", courier, monospace; background-color: #ffffff; /*white-space: pre;*/ } .csharpcode pre { margin: 0em; } .csharpcode .rem { color: #008000; } .csharpcode .kwrd { color: #0000ff; } .csharpcode .str { color: #006080; } .csharpcode .op { color: #0000c0; } .csharpcode .preproc { color: #cc6633; } .csharpcode .asp { background-color: #ffff00; } .csharpcode .html { color: #800000; } .csharpcode .attr { color: #ff0000; } .csharpcode .alt { background-color: #f4f4f4; width: 100%; margin: 0em; } .csharpcode .lnum { color: #606060; } And the resulting HTML: <label id="Order_ShipAddress_Label" for="Order_ShipAddress">Ship Address:</label> <input type="text" value="Rua do Paço, 67" name="Order.ShipAddress" id="Order_ShipAddress" class="class-name"> Now let’s do the same thing except here we’ll use the newly written extension method: @this.TextBox("Order.ShipAddress").Label("Ship Address:") .Class("class-name").IncludeUnobtrusiveValidationAttributes(Html) .csharpcode, .csharpcode pre { font-size: small; color: black; font-family: consolas, "Courier New", courier, monospace; background-color: #ffffff; /*white-space: pre;*/ } .csharpcode pre { margin: 0em; } .csharpcode .rem { color: #008000; } .csharpcode .kwrd { color: #0000ff; } .csharpcode .str { color: #006080; } .csharpcode .op { color: #0000c0; } .csharpcode .preproc { color: #cc6633; } .csharpcode .asp { background-color: #ffff00; } .csharpcode .html { color: #800000; } .csharpcode .attr { color: #ff0000; } .csharpcode .alt { background-color: #f4f4f4; width: 100%; margin: 0em; } .csharpcode .lnum { color: #606060; } And the resulting HTML: <label id="Order_ShipAddress_Label" for="Order_ShipAddress">Ship Address:</label> <input type="text" value="Rua do Paço, 67" name="Order.ShipAddress" id="Order_ShipAddress" data-val-required="The ShipAddress field is required." data-val-length-max="12" data-val-length="The field ShipAddress must be a string with a maximum length of 12." data-val="true" class="class-name"> .csharpcode, .csharpcode pre { font-size: small; color: black; font-family: consolas, "Courier New", courier, monospace; background-color: #ffffff; /*white-space: pre;*/ } .csharpcode pre { margin: 0em; } .csharpcode .rem { color: #008000; } .csharpcode .kwrd { color: #0000ff; } .csharpcode .str { color: #006080; } .csharpcode .op { color: #0000c0; } .csharpcode .preproc { color: #cc6633; } .csharpcode .asp { background-color: #ffff00; } .csharpcode .html { color: #800000; } .csharpcode .attr { color: #ff0000; } .csharpcode .alt { background-color: #f4f4f4; width: 100%; margin: 0em; } .csharpcode .lnum { color: #606060; } Excellent!  Now we can continue to use unobtrusive validation and have the flexibility to use ASP.NET MVC’s Html helpers or MvcContrib’s fluent html helpers interchangeably, and every element will participate in client side validation. Wrap Up Overall I’m happy with this solution, although in the best case scenario MvcContrib would know about unobtrusive validation attributes and include them automatically (of course if it is enabled in the web.config file).  I know that MvcContrib allows you to author global behaviors, but that requires changing the base class of your views, which I am not willing to do. Enjoy!

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• Combining HBase and HDFS results in Exception in makeDirOnFileSystem

  - by utrecht

  Introduction An attempt to combine HBase and HDFS results in the following: 2014-06-09 00:15:14,777 WARN org.apache.hadoop.hbase.HBaseFileSystem: Create Dir ectory, retries exhausted 2014-06-09 00:15:14,780 FATAL org.apache.hadoop.hbase.master.HMaster: Unhandled exception. Starting shutdown. java.io.IOException: Exception in makeDirOnFileSystem at org.apache.hadoop.hbase.HBaseFileSystem.makeDirOnFileSystem(HBaseFile System.java:136) at org.apache.hadoop.hbase.master.MasterFileSystem.checkRootDir(MasterFi leSystem.java:428) at org.apache.hadoop.hbase.master.MasterFileSystem.createInitialFileSyst emLayout(MasterFileSystem.java:148) at org.apache.hadoop.hbase.master.MasterFileSystem.<init>(MasterFileSyst em.java:133) at org.apache.hadoop.hbase.master.HMaster.finishInitialization(HMaster.j ava:572) at org.apache.hadoop.hbase.master.HMaster.run(HMaster.java:432) at java.lang.Thread.run(Thread.java:744) Caused by: org.apache.hadoop.security.AccessControlException: Permission denied: user=hbase, access=WRITE, inode="/":vagrant:supergroup:drwxr-xr-x at org.apache.hadoop.hdfs.server.namenode.FSPermissionChecker.check(FSPe rmissionChecker.java:224) at org.apache.hadoop.hdfs.server.namenode.FSPermissionChecker.check(FSPe rmissionChecker.java:204) at org.apache.hadoop.hdfs.server.namenode.FSPermissionChecker.checkPermi ssion(FSPermissionChecker.java:149) at org.apache.hadoop.hdfs.server.namenode.FSNamesystem.checkPermission(F SNamesystem.java:4891) at org.apache.hadoop.hdfs.server.namenode.FSNamesystem.checkPermission(F SNamesystem.java:4873) at org.apache.hadoop.hdfs.server.namenode.FSNamesystem.checkAncestorAcce ss(FSNamesystem.java:4847) at org.apache.hadoop.hdfs.server.namenode.FSNamesystem.mkdirsInternal(FS Namesystem.java:3192) at org.apache.hadoop.hdfs.server.namenode.FSNamesystem.mkdirsInt(FSNames ystem.java:3156) at org.apache.hadoop.hdfs.server.namenode.FSNamesystem.mkdirs(FSNamesyst em.java:3137) at org.apache.hadoop.hdfs.server.namenode.NameNodeRpcServer.mkdirs(NameN odeRpcServer.java:669) at org.apache.hadoop.hdfs.protocolPB.ClientNamenodeProtocolServerSideTra nslatorPB.mkdirs(ClientNamenodeProtocolServerSideTranslatorPB.java:419) at org.apache.hadoop.hdfs.protocol.proto.ClientNamenodeProtocolProtos$Cl ientNamenodeProtocol$2.callBlockingMethod(ClientNamenodeProtocolProtos.java:4497 0) at org.apache.hadoop.ipc.ProtobufRpcEngine$Server$ProtoBufRpcInvoker.cal l(ProtobufRpcEngine.java:453) at org.apache.hadoop.ipc.RPC$Server.call(RPC.java:1002) at org.apache.hadoop.ipc.Server$Handler$1.run(Server.java:1752) at org.apache.hadoop.ipc.Server$Handler$1.run(Server.java:1748) at java.security.AccessController.doPrivileged(Native Method) at javax.security.auth.Subject.doAs(Subject.java:422) at org.apache.hadoop.security.UserGroupInformation.doAs(UserGroupInforma tion.java:1438) at org.apache.hadoop.ipc.Server$Handler.run(Server.java:1746) at sun.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method) at sun.reflect.NativeConstructorAccessorImpl.newInstance(NativeConstruct orAccessorImpl.java:62) at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingC onstructorAccessorImpl.java:45) at java.lang.reflect.Constructor.newInstance(Constructor.java:408) at org.apache.hadoop.ipc.RemoteException.instantiateException(RemoteExce ption.java:90) at org.apache.hadoop.ipc.RemoteException.unwrapRemoteException(RemoteExc eption.java:57) at org.apache.hadoop.hdfs.DFSClient.primitiveMkdir(DFSClient.java:2153) at org.apache.hadoop.hdfs.DFSClient.mkdirs(DFSClient.java:2122) at org.apache.hadoop.hdfs.DistributedFileSystem.mkdirs(DistributedFileSy stem.java:545) at org.apache.hadoop.fs.FileSystem.mkdirs(FileSystem.java:1915) at org.apache.hadoop.hbase.HBaseFileSystem.makeDirOnFileSystem(HBaseFile System.java:129) ... 6 more while configuration and system settings are as follows: [vagrant@localhost hadoop-hdfs]$ hadoop fs -ls hdfs://localhost/ Found 1 items -rw-r--r-- 3 vagrant supergroup 1010827264 2014-06-08 19:01 hdfs://localhost/u buntu-14.04-desktop-amd64.iso [vagrant@localhost hadoop-hdfs]$ /etc/hadoop/conf/core-site.xml <configuration> <property> <name>fs.defaultFS</name> <value>hdfs://localhost:8020</value> </property> </configuration> /etc/hbase/conf/hbase-site.xml <configuration> <property> <name>hbase.rootdir</name> <value>hdfs://localhost:8020/hbase</value> </property> <property> <name>hbase.cluster.distributed</name> <value>true</value> </property> </configuration> /etc/hadoop/conf/hdfs-site.xml <configuration> <property> <name>dfs.name.dir</name> <value>/var/lib/hadoop-hdfs/cache</value> </property> <property> <name>dfs.data.dir</name> <value>/tmp/hellodatanode</value> </property> </configuration> NameNode directory permissions [vagrant@localhost hadoop-hdfs]$ ls -ltr /var/lib/hadoop-hdfs/cache total 8 -rwxrwxrwx. 1 hbase hdfs 15 Jun 8 23:43 in_use.lock drwxrwxrwx. 2 hbase hdfs 4096 Jun 8 23:43 current [vagrant@localhost hadoop-hdfs]$ HMaster is able to start if fs.defaultFS property has been commented in core-site.xml NameNode is listening [vagrant@localhost hadoop-hdfs]$ netstat -nato | grep 50070 tcp 0 0 0.0.0.0:50070 0.0.0.0:* LIST EN off (0.00/0/0) tcp 0 0 33.33.33.33:50070 33.33.33.1:57493 ESTA BLISHED off (0.00/0/0) and accessible by navigating to http://33.33.33.33:50070/dfshealth.jsp. Question How to solve makeDirOnFileSystem exception and let HBase connect to HDFS?

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• Validating Data Using Data Annotation Attributes in ASP.NET MVC

  - by bipinjoshi

  The data entered by the end user in various form fields must be validated before it is saved in the database. Developers often use validation HTML helpers provided by ASP.NET MVC to perform the input validations. Additionally, you can also use data annotation attributes from the System.ComponentModel.DataAnnotations namespace to perform validations at the model level. Data annotation attributes are attached to the properties of the model class and enforce some validation criteria. They are capable of performing validation on the server side as well as on the client side. This article discusses the basics of using these attributes in an ASP.NET MVC application.http://www.bipinjoshi.net/articles/0a53f05f-b58c-47b1-a544-f032f5cfca58.aspx       

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• Gilda Garretón, a Java Developer and Parallelism Computing Researcher

  - by Yolande

  In a new interview titled “Gilda Garretón, a Java Developer and Parallelism Computing Research,” Garretón shares her first-hand experience developing with Java and Java 7 for very large-scale integration (VLSI) of computer-aided design (CAD). Garretón gives an insightful overview of how Java is contributing to the parallelism development and to the Electric VLSI Design Systems, an open source VLSI CAD application used as a research platform for new CAD algorithms as well as the research flow for hardware test chips.  Garretón considers that parallelism programming is hard and complex, yet important developments are taking place.  "With the addition of the concurrent package in Java SE 6 and the Fork/Join feature in Java SE 7, developers have a chance to rely more on existing frameworks and dedicate more time to the essence of their parallel algorithms." Read the full article here  

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• What are the ways to start making actual/real-world programs using Java/C++ to excel my Programming Skills?

  - by Umer Hassan

  The programming that we learn at university is not that vast, like those are really small exercises to build our logic, but everyone knows that this will not be the scenario when I'll get out in the market as a professional programmer, I really want to make real life programs which would actual make some impacts and will be useful. Tell me in the light of your experience that how should I start making those programs and polish my self as a professional programmer, if there are any sources available for it then kindly also recommend me those.

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• OpenGL: Attempt to allocate a texture to big for the current hardware

  - by AnonymousMan

  I'm getting the following error: java.io.IOException: Attempt to allocate a texture to big for the current hardware at org.newdawn.slick.opengl.InternalTextureLoader.getTexture(InternalTextureLoader.java:320) at org.newdawn.slick.opengl.InternalTextureLoader.getTexture(InternalTextureLoader.java:254) at org.newdawn.slick.opengl.InternalTextureLoader.getTexture(InternalTextureLoader.java:200) at org.newdawn.slick.opengl.TextureLoader.getTexture(TextureLoader.java:64) at org.newdawn.slick.opengl.TextureLoader.getTexture(TextureLoader.java:24) The image I'm trying to use is 128x128. System.out.println(GL11.glGetInteger(GL11.GL_MAX_TEXTURE_SIZE)); I get: 32. 32??!! My graphics card is AMD Radeon HD 7970M with 2048 MB GDDR5 RAM, I can run all the latest games in 1080p and 60fps with no problem, and those textures sure as hell doesn't look like they are 32x32 pixels to me! How can I fix this? -- Edit: Here's the chaos code I use to init OpenGL: Display.setDisplayMode(new DisplayMode(500,500)); Display.create(); if (!GLContext.getCapabilities().OpenGL11) { throw new Exception("OpenGL 1.1 not supported."); } Display.setTitle("Game"); glMatrixMode(GL_PROJECTION); glLoadIdentity(); GLU.gluPerspective(45, 1, 0.1f, 5000); Mouse.setGrabbed(true); glMatrixMode(GL_MODELVIEW); glLoadIdentity(); glEnable(GL_TEXTURE_2D); glClearColor(0, 0, 0, 0); glEnable(GL_DEPTH_TEST); glDepthFunc(GL_LEQUAL); glHint(GL_PERSPECTIVE_CORRECTION_HINT, GL_NICEST); glBlendFunc(GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA); glEnable(GL_BLEND); glEnable(GL_POINT_SMOOTH); glEnable(GL_LINE_SMOOTH); glEnable(GL_POLYGON_SMOOTH); glEnable(GL_POLYGON_OFFSET_FILL); glShadeModel(GL_SMOOTH); Display is a LWJGL thing, it makes the OpenGL context and the window. Anyway, I don't think there's anything in the init code that can help me but you never know...

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• Java 7 Adoption at 79%

  - by Henrik Stahl

  According to a recent blog post from the cloud hosting company Jelastic, Java 7 adoption on their platform is now at 79%. While this is a single data point and should not be read too broadly, it does match other indicators we have that Java 7 is picking up, such as uptake among Oracle middleware customers, download statistics and online activity. The spike in adoption in April coincided with the release of JDK 7 Update 4. This is in line with our expectations since that release added Mac OS X support as well as java.com moving to Java 7 as the default download for end-users; two events that marked the maturity of Java 7 to the community. Since the original release of Java 7, Oracle has shipped 7 update releases, added ports to Mac OSX and Linux/ARM and expanded JavaFX to all common desktop platforms.

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• Is Java viable for serious game development?

  - by tehtros

  Ever since I was a little kid, my dream has been to develop games. Well, now that I am older, more mature, and have some programming experience, I would like to start. However, I would like to turn this into a career. The problem, is that my language of choice is Java. Now, I am not intending this to be a Java vs. C++ question, but rather, is Java an acceptable language for serious game development, instead of lower level languages like C++. By serious, I mean high quality graphics, and being able to play a game with said high quality graphics, without much lag on decent computers. Also, eventually, possible making it to consoles. I have scoured the internet, but there are not very many resources for Java game development, not nearly as many as C++. In fact, most engines are written in C++. Once, I tried to play a made with jMonkeyEngine. The game was terribly slow, to the point where my computer froze. I had no other Java applications running and nothing too resource intensive. Keep in mind, that my computer can play most modern 3D games with ease. So, I am really serious about game development, is Java still a viable choice? I have tried multiple times to learn C++, but I don't really like the language. I don't really know why, but usually, whenever I try to learn, I can never grasp the topics. Also, my most of my friends know Java, and one is even anti-C++, saying that no one knows how to use it right. Then, he goes to say that "there is no right way to use C++, that it can not be used correctly. The nature of the language prevents good code." Also, if I continue to learn and improve Java now, and it turns out that later I am required to learn C++, will making the switch be difficult? So, in short, can Java be taken serious, for serious game development. This includes heavy graphics, fast game play without lag, and possibly, and easy switch to consoles?

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• Java regex patterns - compile time constants or instance members?

  - by KepaniHaole

  Currently, I have a couple of singleton objects where I'm doing matching on regular expressions, and my Patterns are defined like so: class Foobar { private final Pattern firstPattern = Pattern.compile("some regex"); private final Pattern secondPattern = Pattern.compile("some other regex"); // more Patterns, etc. private Foobar() {} public static Foobar create() { /* singleton stuff */ } } But I was told by someone the other day that this is bad style, and Patterns should always be defined at the class level, and look something like this instead: class Foobar { private static final Pattern FIRST_PATTERN = Pattern.compile("some regex"); private static final Pattern SECOND_PATTERN = Pattern.compile("some other regex"); // more Patterns, etc. private Foobar() {} public static Foobar create() { /* singleton stuff */ } } The lifetime of this particular object isn't that long, and my main reason for using the first approach is because it doesn't make sense to me to hold on to the Patterns once the object gets GC'd. Any suggestions / thoughts?

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• How I use RegExp in my Java program? [migrated]

  - by MIH1406

  I have the following string examples: 00001 1 12 123 00002 3 7 321 00003 99 23 332 00004 192 50 912 In a separate text file. Numbers are separated by tabs not spaces. I tried to read the file and print each line if it matches a given RegExp, but I could not find the suitable RegExp for these lines. private static void readFile() { String fileName = "processes.lst"; FileReader file = null; String result = ""; try { file = new FileReader(fileName); BufferedReader reader = new BufferedReader(file); String line = null; String regEx = "[0-9]\t[0-9]\t[0-9]\t[0-9]"; while((line = reader.readLine()) != null) { if(line.matches(regEx)) { result += "\n" + line; } } } catch(Exception e) { System.out.println(e.getMessage()); } finally { if(file != null) try { file.close(); } catch(Exception e) { System.out.println(e.getMessage()); } } System.out.println(result); } I ended up without any string being printed!!

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• Devoxx 2011: Java EE 6 Hands-on Lab Delivered

  - by arungupta

  I, along with Alexis's help, delivered a Java EE 6 hands-on lab to a packed room of about 40+ attendees at Devoxx 2011. The lab was derived from the OTN Developer Days 2012 version but added lot more content to showcase several Java EE 6 technologies. The problem statement from the lab document states: This hands-on lab builds a typical 3-tier Java EE 6 Web application that retrieves customer information from a database and displays it in a Web page. The application also allows new customers to be added to the database as well. The string-based and type-safe queries are used to query and add rows to the database. Each row in the database table is published as a RESTful resource and is then accessed programmatically. Typical design patterns required by a Web application like validation, caching, observer, partial page rendering, and cross-cutting concerns like logging are explained and implemented using different Java EE 6 technologies. The lab covered Java Persistence API 2, Servlet 3, Enterprise JavaBeans 3.1, JavaServer Faces 2, Java API for RESTful Web Services 1.1, Contexts and Dependency Injection 1.0, and Bean Validation 1.0 over 47 pages of detailed self-paced instructions. Here is the complete Table of Contents: The lab can be downloaded from here and requires only NetBeans IDE "All" or "Java EE" version, which includes GlassFish anyway. All the feedback received from the lab has been incorporated in the instructions and bugs filed (Updated 49559, 205232, 205248, 205256). 80% of the attendees could easily complete the lab and some even completed in much less than 3 hours. That indicates that either more content needs to be added to the lab or the intellectual level of the attendees at the conference was pretty high. I think the lab has enough content for 3 hours but we moved at a much more faster pace so I conclude on the latter. Truly a joy to conduct a lab to 40 Devoxxians! Another related lab that might be handy for folks is "Develop, Deploy, and Monitor your Java EE 6 applications using GlassFish 3.1 Cluster". It explains how: Create a 2-instance GlassFish cluster Front-end with a Web server and a load balancer Demonstrate session replication and fail over Monitor the application using JavaScript The complete lab instructions and source code are available and you can try them. I plan to continue evolving the contents for the Java EE 6 hands-on lab to cover more technologies and features and will announce them on this blog. Let me know on what else would you like to see in the future versions.

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