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  • JPA @version - can it be used to calcualate version of a table entry

    - by OpenSource
    Hi, Please consider the following table (created using a corresponding entity) request ------- id requestor type version items 1 a t1 1 5 2 a t1 2 3 3 b t1 1 2 4 a t2 1 4 5 a t1 3 9 The above is what I want to achieve. The version field is a calculated field others are user provided. Basically the request's version needs to be calculated based on the combination of requestor and the type. The first occurance with a given combination will have a version 1 then version 2 and so on. I tried various things using @version on a different entity with just the three columns and joining the two entities using ManytoOne etc but I'm not able to get to the desired outcome. I dont want to confuse you with the things I tried. Since the objective is simple there should be an easier way I suppose? Can you please help? - any help greatly appreciated! thanks in advance

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  • Third Party Libraries and Technologies very Java Programmer must be aware of?

    - by kunjaan
    I agree that this is a very subjective question but as a student of Java , I get suggested good libraries and technologies for Java by my mentors at work. For example, I was not aware of Google Guice for Dependency Injection, awesomeness of Java Reflection APIs, ORMs like Hibernate or stuffs you could do with libraries like Hadoop. I want to collect and share some of the libraries that exemplifies good java programming (so that beginners like me could code walk and emulate the coding practice), teach unique concepts to Java (for example Dependency Injections or ORM) and/or are really interesting libraries that a student like me would get to do interesting projects on (eg. Hadoop). I redited this question 3 times to make it more specific : ). I am sorry if I am really not clear in my intentions. But some kind of a list of good concepts and third party libraries for Java could really help some of my intern friends here at work. Thank you.

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  • Returning a href within a string

    - by user701254
    How can I return a href within a string, I can access the start position but not sure how to get last position : Here is what I have so far : String str = "sadf ad fas dfa http:\\www.google.com sdfa sadf as dfas"; int index = str.indexOf("http"); String href = str.substring(index , ???); What should the end index be ? Note, this is targeted at j2me & I need to minimise download footprint so I cannot use regular expressions or third party regular expressions libraries.

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  • Third Party Libraries and Technologies every Java Programmer must be aware of?

    - by kunjaan
    I agree that this is a very subjective question but as a student of Java , I get suggested good libraries and technologies for Java by my mentors at work. For example, I was not aware of Google Guice for Dependency Injection, awesomeness of Java Reflection APIs, ORMs like Hibernate or stuffs you could do with libraries like Hadoop. I want to collect and share some of the libraries that exemplifies good java programming (so that beginners like me could code walk and emulate the coding practice), teach unique concepts to Java (for example Dependency Injections or ORM) and/or are really interesting libraries that a student like me would get to do interesting projects on (eg. Hadoop). I redited this question 3 times to make it more specific : ). I am sorry if I am really not clear in my intentions. But some kind of a list of good concepts and third party libraries for Java could really help some of my intern friends here at work. Thank you.

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  • Can pydoc/help() hide the documentation for inherited class methods and attributes?

    - by EOL
    When declaring a class that inherits from a specific class: class C(dict): added_attribute = 0 the documentation for class C lists all the methods of dict (either through help(C) or pydoc). Is there a way to hide the inherited methods from the automatically generated documentation (the documentation string can refer to the base class, for non-overwritten methods)? or is it impossible? This would be useful: pydoc lists the functions defined in a module after its classes. Thus, when the classes have a very long documentation, a lot of less than useful information is printed before the new functions provided by the module are presented, which makes the documentation harder to exploit (you have to skip all the documentation for the inherited methods until you reach something specific to the module being documented).

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  • Why did you stop using Tapestry?

    - by ntownsend
    This question goes out to those who have used Tapestry as a web framework and then either gave it up or switched to something else, or even ported their application from Tapestry to something else. The question is why? What led you to make this change? EDIT: Also, what framework (if any) did you change to?

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  • JDBC Pagination

    - by Zeeshan
    Hi, I want to implement pagination using JDBC. The actual thing I want to know is "How can i get first 50 and then next 50 records from database for page 1 and 2 respectively" My Query is Select * from data [data table contains 20,000 rows] For page #1 I get 50 records and for page #2 I want to get next 50 records. How can I implement it efficiently in JDBC? I have searched and found that rs.absolute(row) is the way to skip first page records but it takes some amount of time on large result sets and I don't want to bear this amount of time. Also, I don't want to use rownum and limit + offset in query because these are not good to use in query, I dont know why, still I don't want to use it in query. Can anyone help me how to get limited ResultSet for pagination or is there any way JDBC is giving us?

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  • How do I run compiled java classes with GPU libraries (Jogamp JOCL)?

    - by jam383
    Does anyone know how to run the java code from the command line with dependency on GPU libraries in this case Jogamps JOCL. I have compiled a test program HelloJOCL.java but I get an error during run time. I tried javac -classpath "./lib/jocl.jar:./lib/jocl-natives-macosx-universal.jar:./lib/jocl-natives-linux-i586.jar:./lib/jocl-natives-linux-amd64.jar:./lib/gluegen-rt.jar:./lib/gluegen-rt-natives-linux-amd64.jar:./lib/gluegen-rt-natives-macosx-universal.jar:./lib/gluegen-rt-natives-linux-i586.jar" ./HelloJOCL.java java -classpath "./lib/jocl.jar:./lib/jocl-natives-macosx-universal.jar:./lib/jocl-natives-linux-i586.jar:./lib/jocl-natives-linux-amd64.jar:./lib/gluegen-rt.jar:./lib/gluegen-rt-natives-linux-amd64.jar:./lib/gluegen-rt-natives-macosx-universal.jar:./lib/gluegen-rt-natives-linux-i586.jar:." HelloJOCL but get this error Exception in thread "main" java.lang.NoClassDefFoundError: com/jogamp/opencl/CLContext at java.lang.Class.getDeclaredMethods0(Native Method)

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  • two log4j files for EAR with two modules

    - by nicktmro
    Hi, I have an EAR that is made up of two modules. Both expose services and share common code. Imagine that the ear has a common.jar shared by a webservices.war and webapp.war. I use log4j to log the activities. I would like to be able to have two log files (webservices.log and webapp.log) capturing the events that are specific to each of them plus all the stuff that is handled by the common.jar. How should I configure my categories and my appenders to achieve this? At the moment I have the following packages: com.myapp for shared stuff com.myapp.webservices for the webservices and com.myapp.webapp for the webapp. My problem is that I don't know how I can capture the com.myapp (common stuff) in both log files by using a single log4j configuration file. I have tried setting up multiple configuration files but when JBoss would work OK Websphere would break and the other way round... Thank you

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  • Display BLOB (image) through JSP

    - by jMarcel
    I have a code to show a chart o employees. The data (name, phone, photo etc) are stored in SQLServer and displayed through JSP. Showing the data is ok, except the image .jpg (stored in IMAGE=BLOB column). By the way, I've already got the image displayed (see code below), but I dont't know how to put it in the area defined in a .css (see code below, too), since the image got through the resultSet is loaded in the whole page in the browser. Does anyone knows how can I 'frame' the image ? <% Connection con = FactoryConnection_SQL_SERVER.getConnection("empCHART"); Statement stSuper = con.createStatement(); Statement stSetor = con.createStatement(); Blob image = null; byte[] imgData = null; ResultSet rsSuper = stSuper.executeQuery("SELECT * FROM funChart WHERE dept = 'myDept'"); if (rsSuper.next()) { image = rsSuper.getBlob(12); imgData = image.getBytes(1, (int) image.length()); response.setContentType("image/gif"); OutputStream o = response.getOutputStream(); //o.write(imgData); // even here we got the same as below. //o.flush(); //o.close(); --[...] <table style="margin: 0px; margin-top: 15px;"> <tr> <td id="photo"> <img title="<%=rsSuper.getString("empName").trim()%>" src="<%= o.wite(imageData); o.flush(); o.close(); %>" /> </td> </td> <td id="empData"> <h3><%=rsSuper.getString("empName")%></h3> <p><%=rsSuper.getString("Position")%></p> <p>Id:<br/><%=rsSuper.getString("id")%></p> <p>Phone:<br/><%=rsSuper.getString("Phone")%></p> <p>E-Mail:<br/><%=rsSuper.getString("Email")%></p> </td> </table> And here is the fragment supposed to frame the image: #photo { padding: 0px; vertical-align: middle; text-align: center; width: 170px; height: 220px; } Thanks in advance !

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  • J2ME linking interfaces.

    - by user554031
    Hey guys, I've been working with J2ME for a short while, however I've been unable to find anything regarding my query. I'm wanting to link interfaces, I.E A to B to C. Similar to a card layout. Information on each interface changes based on the choices the user made previously. For example City - Cinema - Cinema Listings. The eventual target is to create a MIDlet that displays information from a database (I understand a midlet needs to connect to a servlet which connects to the DB). Thanks in advance for you're time.

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  • How to make Eclipse compile with Java 1.5 in Mac OS X Leopard (10.5)?

    - by whiskeyspider
    I have been developing in Snow Leopard (10.6). I believe I have some Java6-only API features and I'd like to find these. I moved my project to Leopard (10.5) -- since Snow Leopard does not support Java 1.5 -- but I am so far unable to make Eclipse give compile errors for a Java API call which I know to have been added in 1.6. Here is what I have done: Project properties - Java Compiler - set everything to 1.5. Preferences - Java - Installed JREs - selected JVM 1.5.0. Project properties - Java Build Path - Libraries - says JRE System Library [JVM 1.5.0] What am I missing? Is there another way to find Java API calls added in 1.6 when using Eclipse in Snow Leopard? Thanks.

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  • The Next Frontier: Java Embedded @ JavaOne

    - by Kristin Rose
    Normal 0 false false false EN-US X-NONE X-NONE MicrosoftInternetExplorer4 /* Style Definitions */ table.MsoNormalTable {mso-style-name:"Table Normal"; mso-tstyle-rowband-size:0; mso-tstyle-colband-size:0; mso-style-noshow:yes; mso-style-priority:99; mso-style-qformat:yes; mso-style-parent:""; mso-padding-alt:0in 5.4pt 0in 5.4pt; mso-para-margin:0in; mso-para-margin-bottom:.0001pt; mso-pagination:widow-orphan; font-size:11.0pt; font-family:"Calibri","sans-serif"; mso-ascii-font-family:Calibri; mso-ascii-theme-font:minor-latin; mso-fareast-font-family:"Times New Roman"; mso-fareast-theme-font:minor-fareast; mso-hansi-font-family:Calibri; mso-hansi-theme-font:minor-latin; mso-bidi-font-family:"Times New Roman"; mso-bidi-theme-font:minor-bidi;} Now more than ever, the Java platform is the best technology for many embedded use cases. Java’s platform independence, high level of functionality, security, and developer productivity, address the key pain points in building embedded solutions... and that’s not just our opinion. Take a look at the new IDC report on Oracle’s stewardship of Java, “Java: Two and a half Years After the Acquisition” (doc #236309, August 2012). Java already powers around 3 billion devices worldwide, with traditional desktops and servers being only a small portion of that, and the ‘Internet of Things‘ is just really starting to explode. It is estimated that within five years, intelligent and connected embedded devices will outnumber desktops and mobile phones combined, and will generate the majority of the traffic on the Internet. Is your platform and services strategy ready for the coming disruptions and opportunities? It should come as no surprise that Oracle is enthusiastically focused on Java for Embedded .  New this year, Oracle is demonstrating its further commitment to the embedded marketplace by offering, for the first time, a dedicated conference focused on the business aspects of embedded Java: Java Embedded @ JavaOne. Co-located with the technically-focused JavaOne conference, Java Embedded @ JavaOne will run for two days in San Francisco targeting C-level executives, architects, business leaders, and decision makers. With 24 inspired business sessions with expert speakers from 18 prominent companies driving the next generation of Java Embedded business solutions (such as Cinterion, ARM, Hitachi and Rockwell Automation), attendees will learn how Java Embedded technologies and solutions can offer compelling value and a clear path forward to business efficiency and agility. You’ll also see how Oracle’s comprehensive technology portfolio can deliver a complete ‘Machine to Machine’ platform, from device to datacenter, resulting in a highly secure, resilient, high-performance and cost-effective solution. Seating is limited and we expect a lot of interest in this new event, so please register now! Note that if you are already attending the Oracle OpenWorld or JavaOne conferences, you can attend this conference for only $100 more. Watch my video below to find out more. I hope to see you there! Judson Althoff SVP of WWA&C Normal 0 false false false EN-US X-NONE X-NONE MicrosoftInternetExplorer4 /* Style Definitions */ table.MsoNormalTable {mso-style-name:"Table Normal"; mso-tstyle-rowband-size:0; mso-tstyle-colband-size:0; mso-style-noshow:yes; mso-style-priority:99; mso-style-qformat:yes; mso-style-parent:""; mso-padding-alt:0in 5.4pt 0in 5.4pt; mso-para-margin:0in; mso-para-margin-bottom:.0001pt; mso-pagination:widow-orphan; font-size:11.0pt; font-family:"Calibri","sans-serif"; mso-ascii-font-family:Calibri; mso-ascii-theme-font:minor-latin; mso-fareast-font-family:"Times New Roman"; mso-fareast-theme-font:minor-fareast; mso-hansi-font-family:Calibri; mso-hansi-theme-font:minor-latin; mso-bidi-font-family:"Times New Roman"; mso-bidi-theme-font:minor-bidi;} Normal 0 false false false EN-US X-NONE X-NONE MicrosoftInternetExplorer4 /* Style Definitions */ table.MsoNormalTable {mso-style-name:"Table Normal"; mso-tstyle-rowband-size:0; mso-tstyle-colband-size:0; mso-style-noshow:yes; mso-style-priority:99; mso-style-qformat:yes; mso-style-parent:""; mso-padding-alt:0in 5.4pt 0in 5.4pt; mso-para-margin:0in; mso-para-margin-bottom:.0001pt; mso-pagination:widow-orphan; font-size:11.0pt; font-family:"Calibri","sans-serif"; mso-ascii-font-family:Calibri; mso-ascii-theme-font:minor-latin; mso-fareast-font-family:"Times New Roman"; mso-fareast-theme-font:minor-fareast; mso-hansi-font-family:Calibri; mso-hansi-theme-font:minor-latin; mso-bidi-font-family:"Times New Roman"; mso-bidi-theme-font:minor-bidi;}

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  • Java and AppStore receipt verification

    - by user1672461
    I am trying to verify a payment receipt on server side. I am getting a {"status":21002, "exception":"java.lang.IllegalArgumentException"} in return Here is the code: private final static String _sandboxUriStr = "https://sandbox.itunes.apple.com/verifyReceipt"; public static void processPayment(final String receipt) throws SystemException { final BASE64Encoder encoder = new BASE64Encoder(); final String receiptData = encoder.encode(receipt.getBytes()); final String jsonData = "{\"receipt-data\" : \"" + receiptData + "\"}"; System.out.println(receipt); System.out.println(jsonData); try { final URL url = new URL(_productionUriStr); final HttpURLConnection conn = (HttpsURLConnection) url.openConnection(); conn.setRequestMethod("POST"); conn.setDoOutput(true); final OutputStreamWriter wr = new OutputStreamWriter(conn.getOutputStream()); wr.write(jsonData); wr.flush(); // Get the response final BufferedReader rd = new BufferedReader(new InputStreamReader(conn.getInputStream())); String line; while ((line = rd.readLine()) != null) { System.out.println(line); } wr.close(); rd.close(); } catch (IOException e) { throw new SystemException("Error when trying to send request to '%s', %s", _sandboxUriStr, e.getMessage()); } } My receipt looks like this: {\n\t"signature" = "[exactly_1320_characters]";\n\t"purchase-info" = "[exactly_868_characters]";\n\t"environment" = "Sandbox";\n\t"pod" = "100";\n\t"signing-status" = "0";\n} Receipt data with a BASE64 encoded receipt looks like this: Blockquote {"receipt-data" : "[Block_of_chars_76x40+44=3084_chars_total]"} Does someone have an Idea, or sample code how can I get from receipt string to reply JSON, mentioned here: [http://developer.apple.com/library/ios/#documentation/NetworkingInternet/Conceptual/StoreKitGuide/VerifyingStoreReceipts/VerifyingStoreReceipts.html#//apple_ref/doc/uid/TP40008267-CH104-SW1]? Thank you

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  • terminating java applet thread on page unload

    - by Hammad Tariq
    Hello, I have got a problem here in terminating the threads. The problem is that I am using applet thread to access JS DOM and manipulate innerHTML of a span to right the Thread Name as the innerHTML. It works fine until I keep refreshing the page but if I dont give it a sleep of like 200ms and go to another page which dont have any applet on it, it will give me an error in firebug console: document.getElementById("userName") is null What I am suspecting is, although I send an interrupt on stop and I have also tried the same by setting a flag variable of running in run while loop, the thread executes much faster than the time JVM takes to unload it and I get my page changed in browser but applet is still trying to find an element with id userName. Is that true? Is there any work around of it? Is there any way to know how many threads are running at the moment? Is there any kill all command to send on destroy()? I have searched a lot, seen all the API of java threads and applets, couldn't get this to work. Below is the code: import java.applet.Applet; import netscape.javascript.*; //No need to extend JApplet, since we don't add any components; //we just paint. public class firstApplet extends Applet { /** * */ private static final long serialVersionUID = 1L; firstThread first; boolean running = false; public class firstThread extends Thread{ JSObject win; JSObject doc; firstThread second; public firstThread(JSObject window){ this.win = window; } public void run() { try{ System.out.println("running... "); while (!isInterrupted()){ doc = (JSObject) win.getMember("document"); String userName = Thread.currentThread().getName(); //String userName = "John Doe"; String S = "document.getElementById(\"userName\").innerHTML = \""+userName+"\";"; doc.eval(S); Thread.sleep(5); } }catch(Exception e){ System.out.println("exception in first thread... "); e.printStackTrace(); } } } public void init() { System.out.println("initializing... "); } public void start() { System.out.println("starting... "); JSObject window = JSObject.getWindow(this); first = new firstThread(window); first.start(); running = true; } public void stop() { first.interrupt(); first = null; System.out.println("stopping... "); } public void destroy() { if(first != null){ first = null; } System.out.println("preparing for unloading..."); } } Thanks

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  • Android: Use XML Layout for List Cell rather than Java Code Layout (Widgets)

    - by Stephen Finucane
    Hi, I'm in the process of making a music app and I'm currently working on the library functionality. I'm having some problems, however, in working with a list view (In particular, the cells). I'm trying to move from a simple textview layout in each cell that's created within java to one that uses an XML file for layout (Hence keeping the Java file mostly semantic) This is my original code for the cell layout: public View getView(int position, View convertView, ViewGroup parent) { String id = null; TextView tv = new TextView(mContext.getApplicationContext()); if (convertView == null) { music_column_index = musiccursor.getColumnIndexOrThrow(MediaStore.Audio.Media.TITLE); musiccursor.moveToPosition(position); id = musiccursor.getString(music_column_index); music_column_index = musiccursor.getColumnIndexOrThrow(MediaStore.Audio.Media.DISPLAY_NAME); musiccursor.moveToPosition(position); id += "\n" + musiccursor.getString(music_column_index); music_column_index = musiccursor.getColumnIndexOrThrow(MediaStore.Audio.Albums.ALBUM); musiccursor.moveToPosition(position); id += "\n" + musiccursor.getString(music_column_index); tv.setText(id); } else tv = (TextView) convertView; return tv; } And my new version: public View getView(int position, View convertView, ViewGroup parent) { View cellLayout = findViewById(R.id.albums_list_cell); ImageView album_art = (ImageView) findViewById(R.id.album_cover); TextView album_title = (TextView) findViewById(R.id.album_title); TextView artist_title = (TextView) findViewById(R.id.artist_title); if (convertView == null) { music_column_index = musiccursor.getColumnIndexOrThrow(MediaStore.Audio.Albums.ALBUM); musiccursor.moveToPosition(position); album_title.setText(musiccursor.getString(music_column_index)); //music_column_index = musiccursor.getColumnIndexOrThrow(MediaStore.Audio.Media.DISPLAY_NAME); //musiccursor.moveToPosition(position); music_column_index = musiccursor.getColumnIndexOrThrow(MediaStore.Audio.Media.TITLE); musiccursor.moveToPosition(position); artist_title.setText(musiccursor.getString(music_column_index)); } else{ cellLayout = (TextView) convertView; } return cellLayout; } The initialisation (done in the on create file): musiclist = (ListView) findViewById(R.id.PhoneMusicList); musiclist.setAdapter(new MusicAdapter(this)); musiclist.setOnItemClickListener(musicgridlistener); And the respective XML files: (main) <?xml version="1.0" encoding="utf-8"?> <LinearLayout xmlns:android="http://schemas.android.com/apk/res/android" android:orientation="vertical" android:layout_width="fill_parent" android:layout_height="fill_parent"> <ListView android:id="@+id/PhoneMusicList" android:layout_width="fill_parent" android:layout_height="fill_parent" /> <TextView android:id="@android:id/empty" android:layout_width="wrap_content" android:layout_height="0dip" android:layout_weight="1.0" android:text="@string/no_list_data" /> </LinearLayout> (albums_list_cell) <?xml version="1.0" encoding="utf-8"?> <RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android" android:id="@+id/albums_list_cell" android:layout_width="wrap_content" android:layout_height="wrap_content"> <ImageView android:id="@+id/album_cover" android:layout_alignParentLeft="true" android:layout_alignParentTop="true" android:layout_width="50dip" android:layout_height="50dip" /> <TextView android:id="@+id/album_title" android:layout_toRightOf="@+id/album_cover" android:layout_alignParentTop="true" android:layout_width="wrap_content" android:layout_height="wrap_content" /> <TextView android:id="@+id/artist_title" android:layout_toRightOf="@+id/album_cover" android:layout_below="@+id/album_title" android:layout_width="wrap_content" android:layout_height="15dip" /> </RelativeLayout> In theory (based on the tiny bit of Android I've done so far) this should work..it doesn't though. Logcat gives me a null pointer exception at line 96 of the faulty code, which is the album_title.setText line. It could be a problem with my casting but Google tells me this is ok :D Thanks for any help and let me know if you need more info!

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  • Java Synchronized List Deadlock

    - by portoalet
    From Effective Java 2nd edition item 67 page 266-268: The background thread calls s.removeObserver, which attempts to lock observers, but it can’t acquire the lock, because the main thread already has the lock. All the while, the main thread is waiting for the background thread to finish removing the observer, which explains the deadlock. I am trying to find out which threads deadlock in the main method by using ThreadMXBean (http://stackoverflow.com/questions/1102359/programmatic-deadlock-detection-in-java) , but why does it not return the deadlocked threads? I used a new Thread to run the ThreadMXBean detection. public class ObservableSet<E> extends ForwardingSet<E> { public ObservableSet(Set<E> set) { super(set); } private final List<SetObserver<E>> observers = new ArrayList<SetObserver<E>>(); public void addObserver(SetObserver<E> observer) { synchronized(observers) { observers.add(observer); } } public boolean removeObserver(SetObserver<E> observer) { synchronized(observers) { return observers.remove(observer); } } private void notifyElementAdded(E element) { synchronized(observers) { for (SetObserver<E> observer : observers) observer.added(this, element); } } @Override public boolean add(E element) { boolean added = super.add(element); if (added) notifyElementAdded(element); return added; } @Override public boolean addAll(Collection<? extends E> c) { boolean result = false; for (E element : c) result|=add(element); //callsnotifyElementAdded return result; } public static void main(String[] args) { ObservableSet<Integer> set = new ObservableSet<Integer>(new HashSet<Integer>()); final ThreadMXBean threadMxBean = ManagementFactory.getThreadMXBean(); Thread t = new Thread(new Runnable() { @Override public void run() { while( true ) { long [] threadIds = threadMxBean.findDeadlockedThreads(); if( threadIds != null) { ThreadInfo[] infos = threadMxBean.getThreadInfo(threadIds); for( ThreadInfo threadInfo : infos) { StackTraceElement[] stacks = threadInfo.getStackTrace(); for( StackTraceElement stack : stacks ) { System.out.println(stack.toString()); } } } try { System.out.println("Sleeping.."); TimeUnit.MILLISECONDS.sleep(1000); } catch (InterruptedException e) { // TODO Auto-generated catch block e.printStackTrace(); } } } }); t.start(); set.addObserver(new SetObserver<Integer>() { public void added(ObservableSet<Integer> s, Integer e) { ExecutorService executor = Executors.newSingleThreadExecutor(); final SetObserver<Integer> observer = this; try { executor.submit(new Runnable() { public void run() { s.removeObserver(observer); } }).get(); } catch (ExecutionException ex) { throw new AssertionError(ex.getCause()); } catch (InterruptedException ex) { throw new AssertionError(ex.getCause()); } finally { executor.shutdown(); } } }); for (int i = 0; i < 100; i++) set.add(i); } } public interface SetObserver<E> { // Invoked when an element is added to the observable set void added(ObservableSet<E> set, E element); } // ForwardingSet<E> simply wraps another Set and forwards all operations to it.

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  • java - BigDecimal

    - by Mk12
    I was trying to make my own class for currencies using longs, but Apparently I should use BigDecimal (and then whenever I print it just add the $ sign before it). Could someone please get me started? What would be the best way to use BigDecimals for Dollar currencies, like making it at least but no more than 2 decimal places for the cents, etc. The api for BigDecimal is huge, and I don't know which methods to use. Also, BigDecimal has better precision, but isn't that all lost if it passes through a double? if I do new BigDecimal(24.99), how will it be different than using a double? Or should I use the constructor that uses a String instead? EDIT: I decided to use BigDecimals, and then use: private static final java.text.NumberFormat moneyt = java.text.NumberFormat.getCurrencyInstance(); { money.setRoundingMode(RoundingMode.HALF_EVEN); } and then whenever I display the BigDecimals, to use money.format(theBigDecimal). Is this alright? Should I have the BigDecimal rounding it too? Because then it doesn't get rounded before it does another operation.. if so, could you show me how? And how should I create the BigDecimals? new BigDecimal("24.99") ? Well, after many comments to Vineet Reynolds (thanks for keeping coming back and answering), this is what I have decided. I use BigDecimals and a NumberFormat. Here is where I create the NumberFormat instance. private static final NumberFormat money; static { money = NumberFormat.getCurrencyInstance(Locale.CANADA); money.setRoundingMode(RoundingMode.HALF_EVEN); } Here is my BigDecimal: private final BigDecimal price; Whenever I want to display the price, or another BigDecimal that I got through calculations of price, I use: money.format(price) to get the String. Whenever I want to store the price, or a calculation from price, in a database or in a field or anywhere, I use (for a field): myCalculatedResult = price.add(new BigDecimal("34.58")).setScale(2, RoundingMode.HALF_EVEN); .. but I'm thinking now maybe I should not have the NumberFormat round, but when I want to display do this: System.out.print(money.format(price.setScale(2, RoundingMode.HALF_EVEN); That way to ensure the model and things displayed in the view are the same. I don't do: price = price.setScale(2, RoundingMode.HALF_EVEN); Because then it would always round to 2 decimal places and wouldn't be as precise in calculations. So its all solved now, I guess. But is there any shortcut to typing calculatedResult.setScale(2, RoundingMode.HALF_EVEN) all the time? All I can think of is static importing HALF_EVEN... EDIT: I've changed my mind a bit, I think if I store a value, I won't round it unless I have no more operations to do with it, e.g. if it was the final total that will be charged to someone. I will only round things at the end, or whenever necessary, and I will still use NumberFormat for the currency formatting, but since I always want rounding for display, I made a static method for display: public static String moneyFormat(BigDecimal price) { return money.format(price.setScale(2, RoundingMode.HALF_EVEN)); } So values stored in variables won't be rounded, and I'll use that method to display prices.

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  • Trouble Percent-Encoding Spaces in Java

    - by behrk2
    Hi Everyone, I am using the URLUTF8Encoder.java class from W3C (www.w3.org/International/URLUTF8Encoder.java). Currently, it will encode any blank spaces ' ' into plus signs '+'. I am having difficulty modifying the code to percent-encode the blank space into '%20'. Unfortunately, I am not too familiar with hex. Can anyone help me out? I need to modify this snippet... else if (ch == ' ') { // space sbuf.append('+'); in the following code: final static String[] hex = { "%00", "%01", "%02", "%03", "%04", "%05", "%06", "%07", "%08", "%09", "%0A", "%0B", "%0C", "%0D", "%0E", "%0F", "%10", "%11", "%12", "%13", "%14", "%15", "%16", "%17", "%18", "%19", "%1A", "%1B", "%1C", "%1D", "%1E", "%1F", "%20", "%21", "%22", "%23", "%24", "%25", "%26", "%27", "%28", "%29", "%2A", "%2B", "%2C", "%2D", "%2E", "%2F", "%30", "%31", "%32", "%33", "%34", "%35", "%36", "%37", "%38", "%39", "%3A", "%3B", "%3C", "%3D", "%3E", "%3F", "%40", "%41", "%42", "%43", "%44", "%45", "%46", "%47", "%48", "%49", "%4A", "%4B", "%4C", "%4D", "%4E", "%4F", "%50", "%51", "%52", "%53", "%54", "%55", "%56", "%57", "%58", "%59", "%5A", "%5B", "%5C", "%5D", "%5E", "%5F", "%60", "%61", "%62", "%63", "%64", "%65", "%66", "%67", "%68", "%69", "%6A", "%6B", "%6C", "%6D", "%6E", "%6F", "%70", "%71", "%72", "%73", "%74", "%75", "%76", "%77", "%78", "%79", "%7A", "%7B", "%7C", "%7D", "%7E", "%7F", "%80", "%81", "%82", "%83", "%84", "%85", "%86", "%87", "%88", "%89", "%8A", "%8B", "%8C", "%8D", "%8E", "%8F", "%90", "%91", "%92", "%93", "%94", "%95", "%96", "%97", "%98", "%99", "%9A", "%9B", "%9C", "%9D", "%9E", "%9F", "%A0", "%A1", "%A2", "%A3", "%A4", "%A5", "%A6", "%A7", "%A8", "%A9", "%AA", "%AB", "%AC", "%AD", "%AE", "%AF", "%B0", "%B1", "%B2", "%B3", "%B4", "%B5", "%B6", "%B7", "%B8", "%B9", "%BA", "%BB", "%BC", "%BD", "%BE", "%BF", "%C0", "%C1", "%C2", "%C3", "%C4", "%C5", "%C6", "%C7", "%C8", "%C9", "%CA", "%CB", "%CC", "%CD", "%CE", "%CF", "%D0", "%D1", "%D2", "%D3", "%D4", "%D5", "%D6", "%D7", "%D8", "%D9", "%DA", "%DB", "%DC", "%DD", "%DE", "%DF", "%E0", "%E1", "%E2", "%E3", "%E4", "%E5", "%E6", "%E7", "%E8", "%E9", "%EA", "%EB", "%EC", "%ED", "%EE", "%EF", "%F0", "%F1", "%F2", "%F3", "%F4", "%F5", "%F6", "%F7", "%F8", "%F9", "%FA", "%FB", "%FC", "%FD", "%FE", "%FF" }; public static String encode(String s) { StringBuffer sbuf = new StringBuffer(); int len = s.length(); for (int i = 0; i < len; i++) { int ch = s.charAt(i); if ('A' <= ch && ch <= 'Z') { // 'A'..'Z' sbuf.append((char) ch); } else if ('a' <= ch && ch <= 'z') { // 'a'..'z' sbuf.append((char) ch); } else if ('0' <= ch && ch <= '9') { // '0'..'9' sbuf.append((char) ch); } else if (ch == ' ') { // space sbuf.append('+'); } else if (ch == '-' || ch == '_' // unreserved || ch == '.' || ch == '!' || ch == '~' || ch == '*' || ch == '\'' || ch == '(' || ch == ')') { sbuf.append((char) ch); } else if (ch <= 0x007f) { // other ASCII sbuf.append(hex[ch]); } else if (ch <= 0x07FF) { // non-ASCII <= 0x7FF sbuf.append(hex[0xc0 | (ch >> 6)]); sbuf.append(hex[0x80 | (ch & 0x3F)]); } else { // 0x7FF < ch <= 0xFFFF sbuf.append(hex[0xe0 | (ch >> 12)]); sbuf.append(hex[0x80 | ((ch >> 6) & 0x3F)]); sbuf.append(hex[0x80 | (ch & 0x3F)]); } } return sbuf.toString(); } Thanks!

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  • Fun things you can do by mutating Java strings

    - by polygenelubricants
    So I've come around since I asked how to limit setAccessible to only “legitimate” uses and have come to embrace its power for fun. Enabled by its power, of course, is string mutation. import java.lang.reflect.Field; public class Mutator { static void mutate(Object obj, String field, Object newValue) { try { Field f = obj.getClass().getDeclaredField(field); f.setAccessible(true); f.set(obj, newValue); } catch (Exception e) { } } public static void mutate(String from, String to) { mutate(from, "value", to.toCharArray()); mutate(from, "count", to.length()); } public static void main(String args[]) { Mutator.mutate(System.getProperty("line.separator"), "<br/>\n"); System.out.println("Hello world!"); Mutator.mutate(Integer.toString(Integer.MIN_VALUE), "OMG!"); System.out.println(-2147483648); Mutator.mutate(String.valueOf((Object) null), "LOL!"); System.out.println(Arrays.toString(new int[3][])); Mutator.mutate(Arrays.toString(new int[0]), ":("); System.out.println(Arrays.toString(new byte[0])); } } Output (if no exception is thrown): Hello world!<br/> OMG!<br/> [LOL!, LOL!, LOL!]<br/> :(<br/> Let's see what other fun things we can come up with.

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  • Java Polynomial Multiplication with ArrayList

    - by user1506919
    I am having a problem with one of my methods in my program. The method is designed to take 2 arraylists and the perform multiplication between the two like a polynomial. For example, if I was to say list1={3,2,1} and list2={5,6,7}; I am trying to get a return value of 15,28,38,20,7. However, all I can get is an error message that says: Exception in thread "main" java.lang.IndexOutOfBoundsException: Index: 0, Size: 0. I have provided the method below: private static ArrayList<Integer> multiply(ArrayList<Integer> list1,ArrayList<Integer> list2) { ArrayList<Integer> array =new ArrayList<Integer>(list1.size()+list2.size()); for (int i=0;i<array.size();i++) array.add(i, 0); for (int i = 0; i < list1.size(); i++) for (int j = 0; j < list2.size(); j++) array.set(i+j, ((list1.get(i) * list2.get(j))+array.get(i+j))); return array; } Any help with solving this problem is greatly appreciated.

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  • Storing game objects with generic object information

    - by Mick
    In a simple game object class, you might have something like this: public abstract class GameObject { protected String name; // other properties protected double x, y; public GameObject(String name, double x, double y) { // etc } // setters, getters } I was thinking, since a lot of game objects (ex. generic monsters) will share the same name, movement speed, attack power, etc, it would be better to have all that information shared between all monsters of the same type. So I decided to have an abstract class "ObjectData" to hold all this shared information. So whenever I create a generic monster, I would use the same pre-created "ObjectData" for it. Now the above class becomes more like this: public abstract class GameObject { protected ObjectData data; protected double x, y; public GameObject(ObjectData data, double x, double y) { // etc } // setters, getters public String getName() { return data.getName(); } } So to tailor this specifically for a Monster (could be done in a very similar way for Npcs, etc), I would add 2 classes. Monster which extends GameObject, and MonsterData which extends ObjectData. Now I'll have something like this: public class Monster extends GameObject { public Monster(MonsterData data, double x, double y) { super(data, x, y); } } This is where my design question comes in. Since MonsterData would hold data specific to a generic monster (and would vary with what say NpcData holds), what would be the best way to access this extra information in a system like this? At the moment, since the data variable is of type ObjectData, I'll have to cast data to MonsterData whenever I use it inside the Monster class. One solution I thought of is this, but this might be bad practice: public class Monster extends GameObject { private MonsterData data; // <- this part here public Monster(MonsterData data, double x, double y) { super(data, x, y); this.data = data; // <- this part here } } I've read that for one I should generically avoid overwriting the underlying classes variables. What do you guys think of this solution? Is it bad practice? Do you have any better solutions? Is the design in general bad? How should I redesign this if it is? Thanks in advanced for any replies, and sorry about the long question. Hopefully it all makes sense!

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  • Parallel processing via multithreading in Java

    - by Robz
    There are certain algorithms whose running time can decrease significantly when one divides up a task and gets each part done in parallel. One of these algorithms is merge sort, where a list is divided into infinitesimally smaller parts and then recombined in a sorted order. I decided to do an experiment to test whether or not I could I increase the speed of this sort by using multiple threads. I am running the following functions in Java on a Quad-Core Dell with Windows Vista. One function (the control case) is simply recursive: // x is an array of N elements in random order public int[] mergeSort(int[] x) { if (x.length == 1) return x; // Dividing the array in half int[] a = new int[x.length/2]; int[] b = new int[x.length/2+((x.length%2 == 1)?1:0)]; for(int i = 0; i < x.length/2; i++) a[i] = x[i]; for(int i = 0; i < x.length/2+((x.length%2 == 1)?1:0); i++) b[i] = x[i+x.length/2]; // Sending them off to continue being divided mergeSort(a); mergeSort(b); // Recombining the two arrays int ia = 0, ib = 0, i = 0; while(ia != a.length || ib != b.length) { if (ia == a.length) { x[i] = b[ib]; ib++; } else if (ib == b.length) { x[i] = a[ia]; ia++; } else if (a[ia] < b[ib]) { x[i] = a[ia]; ia++; } else { x[i] = b[ib]; ib++; } i++; } return x; } The other is in the 'run' function of a class that extends thread, and recursively creates two new threads each time it is called: public class Merger extends Thread { int[] x; boolean finished; public Merger(int[] x) { this.x = x; } public void run() { if (x.length == 1) { finished = true; return; } // Divide the array in half int[] a = new int[x.length/2]; int[] b = new int[x.length/2+((x.length%2 == 1)?1:0)]; for(int i = 0; i < x.length/2; i++) a[i] = x[i]; for(int i = 0; i < x.length/2+((x.length%2 == 1)?1:0); i++) b[i] = x[i+x.length/2]; // Begin two threads to continue to divide the array Merger ma = new Merger(a); ma.run(); Merger mb = new Merger(b); mb.run(); // Wait for the two other threads to finish while(!ma.finished || !mb.finished) ; // Recombine the two arrays int ia = 0, ib = 0, i = 0; while(ia != a.length || ib != b.length) { if (ia == a.length) { x[i] = b[ib]; ib++; } else if (ib == b.length) { x[i] = a[ia]; ia++; } else if (a[ia] < b[ib]) { x[i] = a[ia]; ia++; } else { x[i] = b[ib]; ib++; } i++; } finished = true; } } It turns out that function that does not use multithreading actually runs faster. Why? Does the operating system and the java virtual machine not "communicate" effectively enough to place the different threads on different cores? Or am I missing something obvious?

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  • Java client listening to WebSphere MQ Server?

    - by user595234
    I need to write a Java client listening to WebSphere MQ Server. Message is put into a queue in the server. I developed this code, but am not sure it is correct or not. If correct, then how can I test it? This is a standalone Java project, no application server support. Which jars I should put into classpath? I have the MQ settings, where I should put into my codes? Standard JMS can skip these settings? confusing .... import javax.jms.Destination; import javax.jms.Message; import javax.jms.MessageConsumer; import javax.jms.MessageListener; import javax.jms.Queue; import javax.jms.QueueConnection; import javax.jms.QueueConnectionFactory; import javax.jms.QueueReceiver; import javax.jms.QueueSession; import javax.jms.Session; import javax.naming.Context; import javax.naming.InitialContext; import javax.naming.NamingException; public class Main { Context jndiContext = null; QueueConnectionFactory queueConnectionFactory = null; QueueConnection queueConnection = null; QueueSession queueSession = null; Queue controlQueue = null; QueueReceiver queueReceiver = null; private String queueSubject = ""; private void start() { try { queueConnection.start(); queueSession = queueConnection.createQueueSession(false, Session.AUTO_ACKNOWLEDGE); Destination destination = queueSession.createQueue(queueSubject); MessageConsumer consumer = queueSession.createConsumer(destination); consumer.setMessageListener(new MyListener()); } catch (Exception e) { e.printStackTrace(); } } private void close() { try { queueSession.close(); queueConnection.close(); } catch (Exception e) { e.printStackTrace(); } } private void init() { try { jndiContext = new InitialContext(); queueConnectionFactory = (QueueConnectionFactory) this.jndiLookup("QueueConnectionFactory"); queueConnection = queueConnectionFactory.createQueueConnection(); queueConnection.start(); } catch (Exception e) { System.err.println("Could not create JNDI API " + "context: " + e.toString()); System.exit(1); } } private class MyListener implements MessageListener { @Override public void onMessage(Message message) { System.out.println("get message:" + message); } } private Object jndiLookup(String name) throws NamingException { Object obj = null; if (jndiContext == null) { try { jndiContext = new InitialContext(); } catch (NamingException e) { System.err.println("Could not create JNDI API " + "context: " + e.toString()); throw e; } } try { obj = jndiContext.lookup(name); } catch (NamingException e) { System.err.println("JNDI API lookup failed: " + e.toString()); throw e; } return obj; } public Main() { } public static void main(String[] args) { new Main(); } } MQ Queue setting <queue-manager> <name>AAA</name> <port>1423</port> <hostname>ddd</hostname> <clientChannel>EEE.CLIENTS.00</clientChannel> <securityClass>PKIJCExit</securityClass> <transportType>1</transportType> <targetClientMatching>1</targetClientMatching> </queue-manager> <queues> <queue-details id="queue-1"> <name>GGGG.NY.00</name> <transacted>false</transacted> <acknowledgeMode>1</acknowledgeMode> <targetClient>1</targetClient> </queue-details> </queues>

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