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  • How do I detect server status in a port scanner java implementation

    - by akz
    I am writing a port scanner in Java and I want to be able to distinct the following 4 use cases: port is open port is open and server banner was read port is closed server is not live I have the following code: InetAddress address = InetAddress.getByName("google.com"); int[] ports = new int[]{21, 22, 23, 80, 443}; for (int i = 0; i < ports.length; i++) { int port = ports[i]; Socket socket = null; try { socket = new Socket(address, port); socket.setSoTimeout(500); System.out.println("port " + port + " open"); BufferedReader reader = new BufferedReader( new InputStreamReader(socket.getInputStream())); String line = reader.readLine(); if (line != null) { System.out.println(line); } socket.close(); } catch (SocketTimeoutException ex) { // port was open but nothing was read from input stream ex.printStackTrace(); } catch (ConnectException ex) { // port is closed ex.printStackTrace(); } catch (IOException e) { e.printStackTrace(); } finally { if (socket != null && !socket.isClosed()) { try { socket.close(); } catch (Exception e) { e.printStackTrace(); } } } } The problem is that I get a ConnectionException both when the port is closed and the server cannot be reached but with a different exception message: java.net.ConnectException: Connection timed out: connect when the connection was never established and java.net.ConnectException: Connection refused: connect when the port was closed so I cannot make the distinction between the two use cases without digging into the actual exception message. Same thing happens when I try a different approach for the socket creation. If I use: socket = new Socket(); socket.setSoTimeout(500); socket.connect(new InetSocketAddress(address, port), 1000); I have the same problem but with the SocketTimeoutException instead. I get a java.net.SocketTimeoutException: Read timed out if port was open but there was no banner to be read and java.net.SocketTimeoutException: connect timed out if server is not live or port is closed. Any ideas? Thanks in advance!

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  • Primary language - QtC++, C#, Java?

    - by Airjoe
    I'm looking for some input, but let me start with a bit of background (for tl;dr skip to end). I'm an IT major with a concentration in networking. While I'm not a CS major nor do I want to program as a vocation, I do consider myself a programmer and do pretty well with the concepts involved. I've been programming since about 6th grade, started out with a proprietary game creation language that made my transition into C++ at college pretty easy. I like to make programs for myself and friends, and have been paid to program for local businesses. A bit about that- I wrote some programs for a couple local businesses in my senior year in high school. I wrote management systems for local shops (inventory, phone/pos orders, timeclock, customer info, and more stuff I can't remember). It definitely turned out to be over my head, as I had never had any formal programming education. It was a great learning experience, but damn was it crappy code. Oh yeah, by the way, it was all vb6. So, I've used vb6 pretty extensively, I've used c++ in my classes (intro to programming up to algorithms), used Java a little bit in another class (had to write a ping client program, pretty easy) and used Java for some simple Project Euler problems to help learn syntax and such when writing the program for the class. I've also used C# a bit for my own simple personal projects (simple programs, one which would just generate an HTTP request on a list of websites and notify if one responded unexpectedly or not at all, and another which just held a list of things to do and periodically reminded me to do them), things I would've written in vb6 a year or two ago. I've just started using Qt C++ for some undergrad research I'm working on. Now I've had some formal education, I [think I] understand organization in programming a lot better (I didn't even use classes in my vb6 programs where I really should have), how it's important to structure code, split into functions where appropriate, document properly, efficiency both in memory and speed, dynamic and modular programming etc. I was looking for some input on which language to pick up as my "primary". As I'm not a "real programmer", it will be mostly hobby projects, but will include some 'real' projects I'm sure. From my perspective: QtC++ and Java are cross platform, which is cool. Java and C# run in a virtual machine, but I'm not sure if that's a big deal (something extra to distribute, possibly a bit slower? I think Qt would require additional distributables too, right?). I don't really know too much more than this, so I appreciate any help, thanks! TL;DR Am an avocational programmer looking for a language, want quick and straight forward development, liked vb6, will be working with database driven GUI apps- should I go with QtC++, Java, C#, or perhaps something else?

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  • Random generates same number in java

    - by user1613360
    This is my java code. import java.io.*; import java.util.*; import java.util.concurrent.TimeUnit; class search { private int numelem; private int[] input=new int[100]; public void setNumofelem() { System.out.println("Enter the total numebr of elements"); Scanner yz=new Scanner(System.in); numelem=yz.nextInt(); } public void randomnumber() throws Exception { int max=500,min=1,n=numelem; Random rand = new Random(); for (int j=0;j < n;j++) { input[j]=rand.nextInt(max)+1; } } public void printinput() { int b=numelem,t=0; while(true) if(b!=0) { System.out.print(" "+input[t]); b--; t++; } else break; } } public class mycode { public static void main(String args[]) throws Exception { search a=new search(); a.setNumofelem(); a.randomnumber(); a.printinput(); } } Now the function randomnumber() just returns the same number.The function executes perfectly if I execute it as a separate java program but fails miserably if I call it using an object.I have also tried the following variations but nothing works everything return the same number. Variation 1: public void randomnumber() throws Exception { int max=500,min=1,n=numelem; Random rand = new Random(); for (int j=0;j < n;j++) { TimeUnit.SECONDS.sleep(1); input[j]=rand.nextInt(max)+1; } } Variation 2: public void randomnumber() throws Exception { int max=500,min=1,n=numelem; Random rand = new Random(); for (int j=0;j < n;j++) { rand.setSeed(System.nanoTime()); input[j]=rand.nextInt(max)+1; } } Variation 3: public void randomnumber() throws Exception { int max=500,min=1,n=numelem; Random rand = new Random(); for (int j=0;j < n;j++) { TimeUnit.SECONDS.sleep(1); rand.setSeed(System.nanoTime()); input[j]=rand.nextInt(max)+1; } } Sample input/Output: Enter the number of elements: 5 23 23 23 23 23 23

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  • java: useful example of a shutdown hook?

    - by Jason S
    I'm trying to make sure my Java application takes reasonable steps to be robust, and part of that involves shutting down gracefully. I am reading about shutdown hooks and I don't actually get how to make use of them in practice. Is there a practical example out there? Let's say I had a really simple application like this one below, which writes numbers to a file, 10 to a line, in batches of 100, and I want to make sure a given batch finishes if the program is interrupted. I get how to register a shutdown hook but I have no idea how to integrate that into my application. Any suggestions? package com.example.test.concurrency; import java.io.File; import java.io.FileNotFoundException; import java.io.FileOutputStream; import java.io.PrintWriter; public class GracefulShutdownTest1 { final private int N; final private File f; public GracefulShutdownTest1(File f, int N) { this.f=f; this.N = N; } public void run() { PrintWriter pw = null; try { FileOutputStream fos = new FileOutputStream(this.f); pw = new PrintWriter(fos); for (int i = 0; i < N; ++i) writeBatch(pw, i); } catch (FileNotFoundException e) { e.printStackTrace(); } finally { pw.close(); } } private void writeBatch(PrintWriter pw, int i) { for (int j = 0; j < 100; ++j) { int k = i*100+j; pw.write(Integer.toString(k)); if ((j+1)%10 == 0) pw.write('\n'); else pw.write(' '); } } static public void main(String[] args) { if (args.length < 2) { System.out.println("args = [file] [N] " +"where file = output filename, N=batch count"); } else { new GracefulShutdownTest1( new File(args[0]), Integer.parseInt(args[1]) ).run(); } } }

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  • Error with my Android Application httpGet

    - by Coombes
    Basically I'm getting a strange issue with my Android application, it's supposed to grab a JSON Array and print out some values, the class looks like this: ShowComedianActivity.class package com.example.connecttest; public class ShowComedianActivity extends Activity{ TextView name; TextView add; TextView email; TextView tel; String id; // Progress Dialog private ProgressDialog pDialog; //JSON Parser class JSONParser jsonParser = new JSONParser(); // Single Comedian url private static final String url_comedian_details = "http://86.9.71.17/connect/get_comedian_details.php"; // JSON Node names private static final String TAG_SUCCESS = "success"; private static final String TAG_COMEDIAN = "comedian"; private static final String TAG_ID = "id"; private static final String TAG_NAME = "name"; private static final String TAG_ADDRESS = "address"; private static final String TAG_EMAIL = "email"; private static final String TAG_TEL = "tel"; public void onCreate(Bundle savedInstanceState){ super.onCreate(savedInstanceState); setContentView(R.layout.show_comedian); // Getting Comedian Details from intent Intent i = getIntent(); // Getting id from intent id = i.getStringExtra(TAG_ID); new GetComedianDetails().execute(); } class GetComedianDetails extends AsyncTask<String, String, String>{ protected void onPreExecute(){ super.onPreExecute(); pDialog = new ProgressDialog(ShowComedianActivity.this); pDialog.setMessage("Fetching Comedian details. Please wait..."); pDialog.setIndeterminate(false); pDialog.setCancelable(true); pDialog.show(); } @Override protected String doInBackground(String... params) { runOnUiThread(new Runnable(){ public void run(){ int success; try{ //Building parameters List<NameValuePair> params = new ArrayList<NameValuePair>(); params.add(new BasicNameValuePair("id",id)); // Getting comedian details via HTTP request // Uses a GET request JSONObject json = jsonParser.makeHttpRequest(url_comedian_details, "GET", params); // Check Log for json response Log.d("Single Comedian details", json.toString()); //JSON Success tag success = json.getInt(TAG_SUCCESS); if(success == 1){ // Succesfully received product details JSONArray comedianObj = json.getJSONArray(TAG_COMEDIAN); //JSON Array // get first comedian object from JSON Array JSONObject comedian = comedianObj.getJSONObject(0); // comedian with id found name = (TextView) findViewById(R.id.name); add = (TextView) findViewById(R.id.add); email = (TextView) findViewById(R.id.email); tel = (TextView) findViewById(R.id.tel); // Set text to details name.setText(comedian.getString(TAG_NAME)); add.setText(comedian.getString(TAG_ADDRESS)); email.setText(comedian.getString(TAG_EMAIL)); tel.setText(comedian.getString(TAG_TEL)); } } catch (JSONException e){ e.printStackTrace(); } } }); return null; } } } And my JSON Parser class looks like: package com.example.connecttest; public class JSONParser { static InputStream is = null; static JSONObject jObj = null; static String json = ""; // constructor public JSONParser() { } // function get json from url // by making HTTP POST or GET method public JSONObject makeHttpRequest(String url, String method, List<NameValuePair> params) { // Making HTTP request try { // check for request method if(method == "POST"){ // request method is POST // defaultHttpClient DefaultHttpClient httpClient = new DefaultHttpClient(); HttpPost httpPost = new HttpPost(url); httpPost.setEntity(new UrlEncodedFormEntity(params)); HttpResponse httpResponse = httpClient.execute(httpPost); HttpEntity httpEntity = httpResponse.getEntity(); is = httpEntity.getContent(); }else if(method == "GET"){ // request method is GET DefaultHttpClient httpClient = new DefaultHttpClient(); String paramString = URLEncodedUtils.format(params, "utf-8"); url += "?" + paramString; HttpGet httpGet = new HttpGet(url); HttpResponse httpResponse = httpClient.execute(httpGet); HttpEntity httpEntity = httpResponse.getEntity(); is = httpEntity.getContent(); } } catch (UnsupportedEncodingException e) { e.printStackTrace(); } catch (ClientProtocolException e) { e.printStackTrace(); } catch (IOException e) { e.printStackTrace(); } try { BufferedReader reader = new BufferedReader(new InputStreamReader( is, "iso-8859-1"), 8); StringBuilder sb = new StringBuilder(); String line = null; while ((line = reader.readLine()) != null) { sb.append(line + "\n"); } is.close(); json = sb.toString(); } catch (Exception e) { Log.e("Buffer Error", "Error converting result " + e.toString()); } // try parse the string to a JSON object try { jObj = new JSONObject(json); } catch (JSONException e) { Log.e("JSON Parser", "Error parsing data " + e.toString()); } // return JSON String return jObj; } } Now when I run a debug it's querying the correct address with ?id=1 on the end of the URL, and when I navigate to that url I get the following JSON Array: {"success":1,"comedian":[{"id":"1","name":"Michael Coombes","address":"5 Trevethenick Road","email":"[email protected]","tel":"xxxxxxxxxxxx"}]} However my app just crashes, the log-cat report looks like this: 03-22 02:05:02.140: E/Trace(3776): error opening trace file: No such file or directory (2) 03-22 02:05:04.590: E/AndroidRuntime(3776): FATAL EXCEPTION: main 03-22 02:05:04.590: E/AndroidRuntime(3776): android.os.NetworkOnMainThreadException 03-22 02:05:04.590: E/AndroidRuntime(3776): at android.os.StrictMode$AndroidBlockGuardPolicy.onNetwork(StrictMode.java:1117) 03-22 02:05:04.590: E/AndroidRuntime(3776): at libcore.io.BlockGuardOs.connect(BlockGuardOs.java:84) 03-22 02:05:04.590: E/AndroidRuntime(3776): at libcore.io.IoBridge.connectErrno(IoBridge.java:127) 03-22 02:05:04.590: E/AndroidRuntime(3776): at libcore.io.IoBridge.connect(IoBridge.java:112) 03-22 02:05:04.590: E/AndroidRuntime(3776): at java.net.PlainSocketImpl.connect(PlainSocketImpl.java:192) 03-22 02:05:04.590: E/AndroidRuntime(3776): at java.net.PlainSocketImpl.connect(PlainSocketImpl.java:459) 03-22 02:05:04.590: E/AndroidRuntime(3776): at java.net.Socket.connect(Socket.java:842) 03-22 02:05:04.590: E/AndroidRuntime(3776): at org.apache.http.conn.scheme.PlainSocketFactory.connectSocket(PlainSocketFactory.java:119) 03-22 02:05:04.590: E/AndroidRuntime(3776): at org.apache.http.impl.conn.DefaultClientConnectionOperator.openConnection(DefaultClientConnectionOperator.java:144) 03-22 02:05:04.590: E/AndroidRuntime(3776): at org.apache.http.impl.conn.AbstractPoolEntry.open(AbstractPoolEntry.java:164) 03-22 02:05:04.590: E/AndroidRuntime(3776): at org.apache.http.impl.conn.AbstractPooledConnAdapter.open(AbstractPooledConnAdapter.java:119) 03-22 02:05:04.590: E/AndroidRuntime(3776): at org.apache.http.impl.client.DefaultRequestDirector.execute(DefaultRequestDirector.java:360) 03-22 02:05:04.590: E/AndroidRuntime(3776): at org.apache.http.impl.client.AbstractHttpClient.execute(AbstractHttpClient.java:555) 03-22 02:05:04.590: E/AndroidRuntime(3776): at org.apache.http.impl.client.AbstractHttpClient.execute(AbstractHttpClient.java:487) 03-22 02:05:04.590: E/AndroidRuntime(3776): at org.apache.http.impl.client.AbstractHttpClient.execute(AbstractHttpClient.java:465) 03-22 02:05:04.590: E/AndroidRuntime(3776): at com.example.connecttest.JSONParser.makeHttpRequest(JSONParser.java:62) 03-22 02:05:04.590: E/AndroidRuntime(3776): at com.example.connecttest.ShowComedianActivity$GetComedianDetails$1.run(ShowComedianActivity.java:89) 03-22 02:05:04.590: E/AndroidRuntime(3776): at android.os.Handler.handleCallback(Handler.java:615) 03-22 02:05:04.590: E/AndroidRuntime(3776): at android.os.Handler.dispatchMessage(Handler.java:92) 03-22 02:05:04.590: E/AndroidRuntime(3776): at android.os.Looper.loop(Looper.java:137) 03-22 02:05:04.590: E/AndroidRuntime(3776): at android.app.ActivityThread.main(ActivityThread.java:4745) 03-22 02:05:04.590: E/AndroidRuntime(3776): at java.lang.reflect.Method.invokeNative(Native Method) 03-22 02:05:04.590: E/AndroidRuntime(3776): at java.lang.reflect.Method.invoke(Method.java:511) 03-22 02:05:04.590: E/AndroidRuntime(3776): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:786) 03-22 02:05:04.590: E/AndroidRuntime(3776): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:553) 03-22 02:05:04.590: E/AndroidRuntime(3776): at dalvik.system.NativeStart.main(Native Method) From this I'm guessing the error is in the jsonParser.makeHttpRequest however I can't for the life of me figure out what's going wrong and was hoping someone brighter than I could illuminate me.

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  • Oredev 2011 Trip Report

    - by arungupta
    Oredev had its seventh annual conference in the city of Malmo, Sweden last week. The name "Oredev" signifies to the part that Malmo is connected with Copenhagen with Oresund bridge. There were about 1000 attendees with several speakers from all over the world. The first two days were hands-on workshops and the next three days were sessions. There were different tracks such as Java, Windows 8, .NET, Smart Phones, Architecture, Collaboration, and Entrepreneurship. And then there was Xtra(ck) which had interesting sessions not directly related to technology. I gave two slide-free talks in the Java track. The first one showed how to build an end-to-end Java EE 6 application using NetBeans and GlassFish. The complete instructions to build the application are explained in detail here. This 3-tier application used Java Persistence API, Enterprsie Java Beans, Servlet, Contexts and Dependency Injection, JavaServer Faces, and Java API for RESTful Services. The source code built during the application can be downloaded here (LINK TBD). The second session, slide-free again, showed how to take a Java EE 6 application into production using GlassFish cluster. It explained: 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 instructions for this session are available here. Oredev has an interesting way of collecting attendee feedback. The attendees drop a green, yellow, or red card in a bucket as they walk out of the session. Not everybody votes but most do. Other than the instantaneous feedback provided on twitter, this mechanism provides a more coarse grained feedback loop as well. The first talk had about 67 attendees (with 23 green and 7 yellow) and the second one had 22 (11 green and 11 yellow). The speakers' dinner is a good highlight of the conference. It is arranged in the historic city hall and the mayor welcomed all the speakers. As you can see in the pictures, it is a very royal building with lots of history behind it. Fortunately the dinner was a buffet with a much better variety unlike last year where only black soup and geese were served, which was quite cultural BTW ;-) The sauna in 85F, skinny dipping in 35F ocean and alternating between them at Kallbadhus is always very Swedish. Also spent a short evening at a friend's house socializing with other speaker/attendees, drinking Glogg, and eating Pepperkakor.  The welcome packet at the hotel also included cinnamon rolls, recommended to drink with cold milk, for a little more taste of Swedish culture. Something different at this conference was how artists from Image Think were visually capturing all the keynote speakers using images on whiteboards. Here are the images captured for Alexis Ohanian (Reddit co-founder and now running Hipmunk): Unfortunately I could not spend much time engaging with other speakers or attendees because was busy preparing a new hands-on lab material. But was able to spend some time with Matthew Mccullough, Micahel Tiberg, Magnus Martensson, Mattias Karlsson, Corey Haines, Patrick Kua, Charles Nutter, Tushara, Pradeep, Shmuel, and several other folks. Here are a few pictures captured from the event: And the complete album here: Thank you Matthias, Emily, and Kathy for putting up a great show and giving me an opportunity to speak at Oredev. I hope to be back next year with a more vibrant representation of Java - the language and the ecosystem!

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  • Oredev 2011 Trip Report

    - by arungupta
    Oredev had its seventh annual conference in the city of Malmo, Sweden last week. The name "Oredev" signifies to the part that Malmo is connected with Copenhagen with Oresund bridge. There were about 1000 attendees with several speakers from all over the world. The first two days were hands-on workshops and the next three days were sessions. There were different tracks such as Java, Windows 8, .NET, Smart Phones, Architecture, Collaboration, and Entrepreneurship. And then there was Xtra(ck) which had interesting sessions not directly related to technology. I gave two slide-free talks in the Java track. The first one showed how to build an end-to-end Java EE 6 application using NetBeans and GlassFish. The complete instructions to build the application are explained in detail here. This 3-tier application used Java Persistence API, Enterprsie Java Beans, Servlet, Contexts and Dependency Injection, JavaServer Faces, and Java API for RESTful Services. The source code built during the application can be downloaded here (LINK TBD). The second session, slide-free again, showed how to take a Java EE 6 application into production using GlassFish cluster. It explained: 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 instructions for this session are available here. Oredev has an interesting way of collecting attendee feedback. The attendees drop a green, yellow, or red card in a bucket as they walk out of the session. Not everybody votes but most do. Other than the instantaneous feedback provided on twitter, this mechanism provides a more coarse grained feedback loop as well. The first talk had about 67 attendees (with 23 green and 7 yellow) and the second one had 22 (11 green and 11 yellow). The speakers' dinner is a good highlight of the conference. It is arranged in the historic city hall and the mayor welcomed all the speakers. As you can see in the pictures, it is a very royal building with lots of history behind it. Fortunately the dinner was a buffet with a much better variety unlike last year where only black soup and geese were served, which was quite cultural BTW ;-) The sauna in 85F, skinny dipping in 35F ocean and alternating between them at Kallbadhus is always very Swedish. Also spent a short evening at a friend's house socializing with other speaker/attendees, drinking Glogg, and eating Pepperkakor.  The welcome packet at the hotel also included cinnamon rolls, recommended to drink with cold milk, for a little more taste of Swedish culture. Something different at this conference was how artists from Image Think were visually capturing all the keynote speakers using images on whiteboards. Here are the images captured for Alexis Ohanian (Reddit co-founder and now running Hipmunk): Unfortunately I could not spend much time engaging with other speakers or attendees because was busy preparing a new hands-on lab material. But was able to spend some time with Matthew Mccullough, Micahel Tiberg, Magnus Martensson, Mattias Karlsson, Corey Haines, Patrick Kua, Charles Nutter, Tushara, Pradeep, Shmuel, and several other folks. Here are a few pictures captured from the event: And the complete album here: Thank you Matthias, Emily, and Kathy for putting up a great show and giving me an opportunity to speak at Oredev. I hope to be back next year with a more vibrant representation of Java - the language and the ecosystem!

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  • New college grad, psychology major, wants to code professionally. Should I get Sun Java-certified?

    - by Anita
    I just graduated from a fairly well-known liberal arts college in May. Interestingly, I majored in psychology, with a concentration in social psychology. In college I took Intro to Computer Science and hated it (used to blame it on myself; now I blame it on the professor :) However, I've always wanted to be a programmer, and finally got my wish by getting hired by a company that was willing to let me learn coding from scratch in exchange for low pay. Well, what do you know, I just got laid off this morning, and need a new job by November to pay the bills. I loved the coding part of my job at the company, and managed to learn enough Java to feel competent in the job and curious to learn more. I think my goal now is to become a professional programmer. I still know very little (never used Swing, for example) but nothing that a good book can't fix. That's the background anyway; sorry for the rambling - I'm still in shock from the layoff :( It seems to me the quickest way to get noticed by companies, without a CS degree, is by getting certification. I'm halfway through studying for the SCJP and can probably sit for an exam in a week or two. Am I right in my assumption that certs will help in my case? And in general, do I have a bat's chance in hell of making it against formally trained programmers? My assets are really just raw intelligence and intense curiosity; well, maybe a love for problem-solving too. Thanks all - feel free to edit/tag the post!

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  • Move a player to another team, with players stored in one arraylist and teams in another using java

    - by user1056758
    Basically I have a team class, which has an array list that store the players in. In the driver class theres an arraylist that stores the teams. Anyhow I've worked out how to add a player to a specific team and like wise remove a player from said team. Where I'm hitting problems is when I try to transfer one player to another. My understanding is to scan through the first team,and get the player. Then some how add this player to another, by scanning through the chosen team and add to it? I've tried this way but it seems to replace the original player with the new player in both teams. My other approach would be to somehow return the parameters of the player object, create another with the return parameters, remove the orignal then add the new instance in the other team? Really not quite generally how I can go about this, been trying all afternoon! If someone could offer me a general idea, then I can go off and apply the understanding to practice. Many thanks

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  • Java: immutable Stack?

    - by HH
    I chose to use Stacks and Tables before knowing Collections has immutable empty things only for Set, Map and List. Because the size of table does not change after its init: Integer[] table = new Intger[0] I can use the zero-witdh table as an empty table. But I cannot use final or empty Stack to get immutable Stack: No immutability to Stack with Final import java.io.*; import java.util.*; public class TestStack{ public static void main(String[] args) { final Stack<Integer> test = new Stack<Integer>(); Stack<Integer> test2 = new Stack<Integer>(); test.push(37707); test2.push(80437707); //WHY is there not an error to remove an elment // from FINAL stack? System.out.println(test.pop()); System.out.println(test2.pop()); } } Java Api 5 for list interface shows that Stack is an implementing class for list and arraylist, here. The java.coccurrent pkg does not have any immutable Stack data structure. From Stack to some immutable data structure How to get immutable Stack data structure? Can I box it with list? Should I switch my current implementatios from stacks to Lists to get immutable? Which immutable data structure is Very fast with about similar exec time as Stack?

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  • Location of Java dump heap file?

    - by Jim Ferrans
    Well this is embarrassing ... I'm starting to play with the Eclipse Memory Analyzer to look for Java memory leaks on a Windows box. Step 1 is to obtain a heap dump file. To do this< I start my Java (javaw.exe) process from within Eclipse and connect to it with jconsole. Then on the jconsole MBeans tab I click the dumpHeap button. The first time I did this, I saw a pop-up saying it had created the heap dump file, but not giving its name or location. Now whenever I do a dumpHeap again while connected to a different javaw.exe process, jconsole says: Problem invoking dumpHeap : java.io.IOException: File exists and of course doesn't give its name or path. Where could it be? I've searched my C: drive (using cygwin command line tools) for files containing "hprof" or "java_pid" or "heapdump" and didn't find anything plausible. I've even used the Windows search to look for all files in my Eclipse workspace that have changed in the last day. I'm using the Sun Java 1.6 JVM, and don't have -XX:HeapDumpPath set.

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  • Java - Trying to log into website with invalid ssl certificate using httpclient

    - by PCBEEF
    I'm trying to log into site with invalid ssl certificate and I have the following code. I bypass the the invalid cert by using my all certificate and then bypass the invalid Hostname by using hostnameverifier. However, the hostnameverifier does not seem to work and I still get the error message javax.net.ssl.SSLException: hostname in certificate didn't match: The code is: public static void main(String[] args) { TrustManager[] trustAllCerts = new TrustManager[] { new X509TrustManager() { public java.security.cert.X509Certificate[] getAcceptedIssuers() { return null; } public void checkClientTrusted( java.security.cert.X509Certificate[] certs, String authType) { } public void checkServerTrusted( java.security.cert.X509Certificate[] certs, String authType) { } } }; HostnameVerifier hv = new HostnameVerifier() { public boolean verify(String urlHostName, SSLSession session) { System.out.println("Warning: URL Host: "+urlHostName+" vs. "+session.getPeerHost()); return true; } }; try { SSLContext sc = SSLContext.getInstance("SSL"); sc.init(null, trustAllCerts, new java.security.SecureRandom()); HttpsURLConnection.setDefaultSSLSocketFactory(sc.getSocketFactory()); HttpsURLConnection.setDefaultHostnameVerifier(hv); } catch (Exception e) { } try { DefaultHttpClient httpclient = new DefaultHttpClient(); HttpContext localContext = new BasicHttpContext(); List<NameValuePair> formparams = new ArrayList<NameValuePair>(); formparams.add(new BasicNameValuePair("username", "user")); formparams.add(new BasicNameValuePair("password", "pword")); UrlEncodedFormEntity entity; entity = new UrlEncodedFormEntity(formparams, "UTF-8"); HttpPost httppost = new HttpPost("https://www.mysite.com/"); httppost.setEntity(entity); HttpResponse response = httpclient.execute(httppost, localContext); } catch (UnsupportedEncodingException e) { e.printStackTrace(); } catch (IOException e) { e.printStackTrace(); } }

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  • Linker errors using LuaJava on OSX 10.5

    - by Daniel
    Hi, I'm having a bunch of problems getting this library to work on my OSX installation. In particular, I'd like to use it with a Java 1.6 VM but after I compile it up I get the following: java -cp "luajava-1.1.jar" org.keplerproject.luajava.Console Exception in thread "main" java.lang.UnsatisfiedLinkError: /Users/dharabor/src/luajava- 1.1/libluajava-1.1.jnilib: at java.lang.ClassLoader$NativeLibrary.load(Native Method) at java.lang.ClassLoader.loadLibrary0(ClassLoader.java:1822) at java.lang.ClassLoader.loadLibrary(ClassLoader.java:1739) at java.lang.Runtime.loadLibrary0(Runtime.java:823) at java.lang.System.loadLibrary(System.java:1030) at org.keplerproject.luajava.LuaState.<clinit>(LuaState.java:92) at org.keplerproject.luajava.LuaStateFactory.newLuaState(LuaStateFactory.java:59) at org.keplerproject.luajava.Console.main(Console.java:49) I'm running OSX 10.5.8 with Lua 5.1.4 I've also changed my OSX default VM to 1.6.0 as so: /System/Library/Frameworks/JavaVM.framework/Home -> Versions/1.6.0/Home/ /System/Library/Frameworks/JavaVM.framework/Versions/Current -> 1.6.0/ /System/Library/Frameworks/JavaVM.framework/Versions/CurrentJDK -> 1.6.0/ What am I doing wrong? I notice when I use Java 1.5 everything works great. Except I don't want 1.5, I want 1.6.

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  • Books and resources for Java Performance tuning - when working with databases, huge lists

    - by Arvind
    Hi All, I am relatively new to working on huge applications in Java. I am working on a Java web service which is pretty heavily used by various clients. The service basically queries the database (hibernate) and then works with a lot of Lists (there are adapters to convert list returned from DB to the interface which the service publishes) and I am seeing lot of issues with the service like high CPU usage or high heap space. While I can troubleshoot the performance issues using a profiler, I want to actually learn about what all I need to take care when I actually write code. Like what kind of List to use or things like using StringBuilder instead of String, etc... Is there any book or blogs which I can refer which will help me while I write new services? Also my application is multithreaded - each service call from a client is a new thread, and I want to know some best practices around that area as well. I did search the web but I found many tips which are not relevant in the latest Java 6 releases, so wanted to know what kind of resources would help a developer starting out now on Java for heavily used applications. Arvind

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  • Why is the user.dir system property working in Java?

    - by Geo
    Almost every article I read told me that you can't have chdir in Java. The accepted answer to this question says you can't do it in Java. However, here's some of the stuff I tried : geo@codebox:~$ java -version java version "1.6.0_14" Java(TM) SE Runtime Environment (build 1.6.0_14-b08) Java HotSpot(TM) Client VM (build 14.0-b16, mixed mode, sharing) Here's a test class I'm using : import java.io.*; public class Ch { public static void main(String[] args) { System.out.println(new File(".").getAbsolutePath()); System.setProperty("user.dir","/media"); System.out.println(new File(".").getAbsolutePath()); } } geo@codebox:~$ pwd /home/geo geo@codebox:~$ java Ch /home/geo/. /media/. Please explain why this worked. Can I use this from now on and expect it to work the same way on all platforms?

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  • Java equivalent to VS solution file

    - by Chris
    I'm a C# guy trying to learn Java. I understand the syntax and the basic architecture of the Java platform, and have no problem doing smaller projects myself, but I'd really like to be able to download some open source projects to learn from the work of others. However, I'm running into a stumbling block that I can't seem to find any information on. When I download an open source .NET project, I can open the .sln file with visual studio and everything just loads. Sure, there's occasionally a missing reference or something, but there's really very little configuration required to get things going. I'm not sensing the same ease of use with Java. I'm using eclipse at the moment, and it feels like for every project I have to create a brand new Eclipse project using "create from existing source", and almost nothing compiles properly without significant reconfiguration. In the case of web projects, it's even worse, because Eclipse doesn't appear to support creating a web project from existing source. I have to create a standard Java project from source, then then apparently modify the project file to include the bindings for the web toolkit stuff to work properly. Assuming I want to be able to contribute to a project later on, I shouldn't have to be making such drastic changes to the file structure to get my IDE to a workable state. What am I missing?

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  • Java FileLock for Reading and Writing

    - by bobtheowl2
    I have a process that will be called rather frequently from cron to read a file that has certain move related commands in it. My process needs to read and write to this data file - and keep it locked to prevent other processes from touching it during this time. A completely separate process can be executed by a user to (potential) write/append to this same data file. I want these two processes to play nice and only access the file one at a time. The nio FileLock seemed to be what I needed (short of writing my own semaphore type files), but I'm having trouble locking it for reading. I can lock and write just fine, but when attempting to create lock when reading I get a NonWritableChannelException. Is it even possible to lock a file for reading? Seems like a RandomAccessFile is closer to what I need, but I don't see how to implement that. Here is the code that fails: FileInputStream fin = new FileInputStream(f); FileLock fl = fin.getChannel().tryLock(); if(fl != null) { System.out.println("Locked File"); BufferedReader in = new BufferedReader(new InputStreamReader(fin)); System.out.println(in.readLine()); ... The exception is thrown on the FileLock line. java.nio.channels.NonWritableChannelException at sun.nio.ch.FileChannelImpl.tryLock(Unknown Source) at java.nio.channels.FileChannel.tryLock(Unknown Source) at Mover.run(Mover.java:74) at java.lang.Thread.run(Unknown Source) Looking at the JavaDocs, it says Unchecked exception thrown when an attempt is made to write to a channel that was not originally opened for writing. But I don't necessarily need to write to it. When I try creating a FileOutpuStream, etc. for writing purposes it is happy until I try to open a FileInputStream on the same file.

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  • saxon java xpath exception :

    - by changed
    Hi I am trying to read XPath queries from a file and run it against a xml data file. I am doing it through Saxon Xpath processor. But i keep getting this error. Code i am using is from sample code provided with the library. Error i am getting is : Exception in thread "main" javax.xml.xpath.XPathExpressionException: Supplied node must be built using the same or a compatible Configuration at net.sf.saxon.xpath.XPathExpressionImpl.evaluate(XPathExpressionImpl.java:283) at net.sf.saxon.xpath.XPathExpressionImpl.evaluate(XPathExpressionImpl.java:375) at edu.xml.XPathExample.go(XPathExample.java:81) at edu.xml.XPathExample.main(XPathExample.java:42) - public void go(String filename) throws Exception { XPathExpression findLine = null; String readLine = null; Object document = new XPathEvaluator().setSource(new StreamSource(new File(dataPath))); System.setProperty("javax.xml.xpath.XPathFactory:" + NamespaceConstant.OBJECT_MODEL_SAXON, "net.sf.saxon.xpath.XPathFactoryImpl"); XPathFactory xpf = XPathFactory.newInstance(NamespaceConstant.OBJECT_MODEL_SAXON); XPath xpe = xpf.newXPath(); if (filename != null) { this.queryPath = filename; } try { fileReader = new BufferedReader(new FileReader(queryPath)); } catch (FileNotFoundException ex) { System.out.println("File not found: " + ex.getMessage()); } xpe.setXPathVariableResolver(this); while (true) { try { readLine = fileReader.readLine(); } catch (IOException ex) { System.out.println("Error while reading file: " + ex.getMessage()); } if (readLine == null) { break; } findLine = xpe.compile(readLine); String resultString = findLine.evaluate(document); System.out.println("<output>"); System.out.println("String Value => " + resultString); System.out.println("</output>"); } }

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  • Making Spring Data JPA work with DataNucleus (GAE) (Spring Boot)

    - by xybrek
    There are several hints that Spring Data works with Google App Engine like: http://tommysiu.blogspot.com/2014/01/spring-data-on-gae-part-1.html http://blog.eisele.net/2009/07/spring-300m3-on-google-appengine-with.html Much of the examples are not "Spring Boot" so I've been trying to retrofit things with it. However, I've been stuck with this error for days and days: [INFO] Caused by: java.lang.NullPointerException [INFO] at org.datanucleus.api.jpa.metamodel.SingularAttributeImpl.isVersion(SingularAttributeImpl.java:79) [INFO] at org.springframework.data.jpa.repository.support.JpaMetamodelEntityInformation.findVersionAttribute(JpaMetamodelEntityInformation.java:102) [INFO] at org.springframework.data.jpa.repository.support.JpaMetamodelEntityInformation.<init>(JpaMetamodelEntityInformation.java:79) [INFO] at org.springframework.data.jpa.repository.support.JpaEntityInformationSupport.getMetadata(JpaEntityInformationSupport.java:65) [INFO] at org.springframework.data.jpa.repository.support.JpaRepositoryFactory.getEntityInformation(JpaRepositoryFactory.java:149) [INFO] at org.springframework.data.jpa.repository.support.JpaRepositoryFactory.getTargetRepository(JpaRepositoryFactory.java:88) [INFO] at org.springframework.data.jpa.repository.support.JpaRepositoryFactory.getTargetRepository(JpaRepositoryFactory.java:68) [INFO] at org.springframework.data.repository.core.support.RepositoryFactorySupport.getRepository(RepositoryFactorySupport.java:158) [INFO] at org.springframework.data.repository.core.support.RepositoryFactoryBeanSupport.initAndReturn(RepositoryFactoryBeanSupport.java:224) [INFO] at org.springframework.data.repository.core.support.RepositoryFactoryBeanSupport.afterPropertiesSet(RepositoryFactoryBeanSupport.java:210) [INFO] at org.springframework.data.jpa.repository.support.JpaRepositoryFactoryBean.afterPropertiesSet(JpaRepositoryFactoryBean.java:92) [INFO] at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory$6.run(AbstractAutowireCapableBeanFactory.java:1602) [INFO] at java.security.AccessController.doPrivileged(Native Method) [INFO] at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.invokeInitMethods(AbstractAutowireCapableBeanFactory.java:1599) [INFO] at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.initializeBean(AbstractAutowireCapableBeanFactory.java:1549) [INFO] ... 40 more Where, I'm trying to use Spring Data JPA with DataNucleus/AppEngine: @Configuration @ComponentScan @EnableJpaRepositories @EnableTransactionManagement class JpaApplicationConfig { private static final Logger logger = Logger .getLogger(JpaApplicationConfig.class.getName()); @Bean public EntityManagerFactory entityManagerFactory() { logger.info("Loading Entity Manager..."); return Persistence .createEntityManagerFactory("transactions-optional"); } @Bean public PlatformTransactionManager transactionManager() { logger.info("Loading Transaction Manager..."); final JpaTransactionManager txManager = new JpaTransactionManager(); txManager.setEntityManagerFactory(entityManagerFactory()); return txManager; } } I've tested Persistence.createEntityManagerFactory("transactions-optional"); to see if the app can persist using this EMF, well, it does, so I am sure that this EMF works fine. The problem is the "wiring" up with the Spring Data JPA, can anybody help?

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  • TLS with SNI in Java clients

    - by ftrotter
    There is an ongoing discussion on the security and trust working group for NHIN Direct regarding the IP-to-domain mapping problem that is created with traditional SSL. If an HISP (as defined by NHIN Direct) wants to host thousands of NHIN Direct "Health Domains" for providers, then it will an "artificially inflated cost" to have to purchase an IP for each of those domains. Because Apache and OpenSSL have recently released TLS with support for the SNI extension, it is possible to use SNI as a solution to this problem on the server side. However, if we decide that we will allow server implementations of the NHINDirect transport layer to support TLS+SNI, then we must require that all clients support SNI too. OpenSSL based clients should do this by default and one could always us stunnel to implement an TLS+SNI aware client to proxy if your given programming language SSL implementation does not support SNI. It appears that native Java applications using OpenJDK do not yet support SNI, but I cannot get a straight answer out of that project. I know that there are OpenSSL Java libraries available but I have no idea if that would be considered viable. Can you give me a "state of the art" summary of where TLS+SNI support is for Java clients? I need a Java implementers perspective on this.

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  • Encryption in Java & Flex

    - by Jef
    I want tp encrypt and decrypt string, with defined salt. But the result must be same if the code run in java and adobe flex. The main goal is: the app in adobe flex will be generate a string that can be decrypt in server using java. I use this flex library http://crypto.hurlant.com/demo/ Try to 'Secret Key' Tab. I want to use AES Encryption, 'CBC' or 'PKCS5'. var k:String = "1234567890123456"; var kdata:ByteArray = Hex.toArray(k); var txt:String = "hello"; var data:ByteArray = Hex.toArray(Hex.fromString(txt));; var name:String = "simple-aes-cbc"; var pad:IPad =new PKCS5(); var mode:ICipher = Crypto.getCipher(name, kdata, pad); pad.setBlockSize(mode.getBlockSize()); mode.encrypt(data); encrypted.text=Hex.fromArray(data); trace(Hex.fromArray(data)); And here is the code in java String plaintext = "hello"; String key = "1234567890123456"; SecretKey keyspec = new SecretKeySpec(key.getBytes(), "AES"); Cipher cipher = Cipher.getInstance("AES/CBC/PKCS5Padding"); cipher.init(Cipher.ENCRYPT_MODE,keyspec); byte[] encrypted = cipher.doFinal(plaintext.getBytes()); BASE64Encoder base64 = new BASE64Encoder(); String encodedString = base64.encode(encrypted); System.out.println(encodedString); Why the result is not same? Can you guys provide the sample with the same result both of java and flex (encrypt and decrypt)? And if I want to change the paramater, for example, from cbc to ebc, which line that need to be changed? Thanks!

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  • Hudson plugin, Java error "... disagree on InnerClasses attribute"

    - by StackedCrooked
    I am trying to be able to step through the code of a Hudson plugin called SVNPublisher. I checked out the code for SVNPublisher, used Netbeans to open the project, and clicked "Debug Main project". This results in a Firefox window opening address http://localhost:8080 which shows the Hudson main page. Clicking the "New Job" link results in an error page: HTTP ERROR: 500 jar:file:/home/francis/svn/svnpublisher/target/work/webapp/WEB-INF/lib/hudson-core-1.319.jar!/lib/hudson/newFromList/form.jelly:43:47: <j:forEach> hudson.scm.SubversionTagAction and hudson.scm.SubversionTagAction$DescriptorImpl disagree on InnerClasses attribute RequestURI=/newJob Caused by: org.apache.commons.jelly.JellyTagException: jar:file:/home/francis/svn/svnpublisher/target/work/webapp/WEB-INF/lib/hudson-core-1.319.jar!/lib/hudson/newFromList/form.jelly:43:47: hudson.scm.SubversionTagAction and hudson.scm.SubversionTagAction$DescriptorImpl disagree on InnerClasses attribute at org.apache.commons.jelly.impl.TagScript.handleException(TagScript.java:713) at org.apache.commons.jelly.impl.TagScript.run(TagScript.java:282) at org.apache.commons.jelly.impl.ScriptBlock.run(ScriptBlock.java:95) ... I am very new to Hudson and not very experienced with Java so I'm pretty much clueless on the meaning of this error. Can anyone help?

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  • Java Robot key activity seems to stop working while certain software is running

    - by Mike Turley
    I'm writing a Java application to automate character actions in an online game overnight (specifically, it catches fish in Final Fantasy XI). The app makes heavy use of java's Robot class both for emulating user keyboard input and for detecting color changes on certain parts of the screen. It also uses multithreading and a swing GUI. The application seems to work perfectly when I test it without the game running, just using screenshots to trigger the apps responses into notepad. But for some reason, when I actually launch FFXI and start the program, all of my keyboard and mouse manipulations just stop working altogether. The program is still running, and the Robot class is still able to read pixel colors. But Robot.keyPress, Robot.keyRelease, Robot.mouseMove, Robot.mousePress and Robot.mouseRelease all do nothing. It's the strangest thing-- to test it, I wrote a simple loop that just keeps typing letters, and focused notepad. I'd then start the game, refocus notepad, and it would do nothing. Then I'd exit the game, and it'd start working again immediately. Has anyone else come across something like this, where specific software will stop certain functions of java from working? Also, to make this more interesting-- Last year I wrote a very similar program using the same classes and programming techniques to automate healing a party in the game as they fight. Last year, this program worked perfectly. After running into these problems I dug up that old program, ran it without making any changes, and found that it too was having the same problems. The only differences between now and when it was working: I was running Windows Vista and now I'm running Windows 7, and several new Java versions as well as FFXI versions have been released. What the hell is going on? (if anyone needs to see my source code, email me at [email protected]. I'm trying to keep it to myself.)

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  • Interpolation of scattered data: What could I do?

    - by Simon
    Hi! I need your help. I'm working on a 3D chart in Java using Java 3D. It should be able to display a bunch of measured values. As measured, the data I get is scattered. This means I will have to interpolate the missing points in order to get my surface plotted nicely. I didn't study all that 3D-Geometry stuff yet and I don't know where to start. My idea is to triangulate the points to a surface and then, based on the triangulation, interpolate the missing points. (see this to have a rough idea of what I want to achieve) Does someone have experiences with the interpolation of scattered data? Is my approach the right one? If yes, what kind of data structures and algorithms will I need in order to triangulate my points cloud?

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  • I/O between AIR client using Native process and executable java .jar

    - by aseem behl
    I am using Adobe AIR 2.0 native process API to launch a java executable jar. I/O is handled by writing to the input stream of the java process and reading from the output stream. The application is event based where several events are fired from the server. We catch these events in java code, handle them and write the output to the outputstream using the synchronized static method below. public class ReaderWriter { static Logger logger = Logger.getLogger(ReaderWriter.class); public synchronized static void writeToAir(String output){ try{ byte[] byteArray = output.getBytes(); DataOutputStream dataOutputStream = new DataOutputStream(System.out); dataOutputStream.write(byteArray); dataOutputStream.flush(); } catch (IOException e) { logger.info("Exception while writing the output. " + e); } } } The issue is that some messages are lost between the transfer and not all messages reach the AIR client. If I run the java application from the console I am receiving all the messages. It would be great if somebody could point out what I am missing. Following are some of the listeners used to send the event data to the AIR client. // class used to process Shutdown events from the Session private class SessionShutdownListener implements SessionListener{ public void onEvent(Event e) { Session.Shutdown sd = (Session.Shutdown) e; Session.ShutdownReason sr = sd.getReason(); String eventOutput = "eo;" + "Session Shutdown event ocurred reason=" + sr.strValue() + "\n"; ReaderWriter.writeToAir(eventOutput); } } // class used to process OperationSucceeded events from the Session private class SessionOperationSucceededListener implements SessionListener{ public void onEvent(Event e) { Session.OperationSucceeded os = (Session.OperationSucceeded) e; String eventOutput = "eo;" + "Session OperationSucceeded event ocurred" + "\n"; ReaderWriter.writeToAir(eventOutput); } }

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