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  • How to use locks/synchronization here

    - by MasterGberry
    I have this code block here and i need to make sure the rankedPlayersWaitingForMatch is synchronized between threads properly. I was going to use synchronize but that i don't think will work here because of the variable being used in the if statement. I read online about final Lock lock = new ReentrantLock(); but I am a bit confused on how to use it in this case properly with the try/finally block. Can I get a quick example? Thanks // start synchronization if (rankedPlayersWaitingForMatch.get(rankedType).size() >= 2) { Player player1 = rankedPlayersWaitingForMatch.get(rankedType).remove(); Player player2 = rankedPlayersWaitingForMatch.get(rankedType).remove(); // end synchronization // ... I don't want this all to be synchronized, just after the first 2 remove() } else { // end synchronization // ... }

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  • How to stop expanding an infinite SWT Tree upon pressing "*"

    - by Lóránt Pintér
    I have an SWT Tree in my application that contains an infinite data structure. Upon expanding an item, I generate its children. On Windows though, users can press "*", triggering an "expand all descendants" action, and my application hangs. There are two acceptable behaviors for me when the user presses "*": Expand all children of the selected element, but only to the next level Do nothing In either case, I will still need to be able to expand items as deep as required (by clicking on the [+] icon, or by pressing "+"), so limiting the tree depth is not a solution. Is there another way that I can achieve either of the above without modifying SWT classes?

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  • How to reference an embedded JCA resource adapater

    - by cg
    For our current J2EE project based on JBoss, we need to interface with a remote system using message driven beans and a JCA resource adapter provided as a RAR file by a third party. I would like to package and deploy the entire project as an EAR file to our JBoss server. Most notably, the RAR file should be embedded within the EAR file and not be deployed globally. All of this is working fine so far, but I'm not particularly happy with the way the RAR file is referenced. The jboss.xml packaged with the MDB for example, currently looks like this: <jboss> <enterprise-beans> <message-driven> <ejb-name>testBean1</ejb-name> <resource-adapter-name>test1.ear#thirdparty-1.0.rar</resource-adapter-name> </message-driven> </enterprise-beans> </jboss> While this is generally working fine, it will break when the EAR file is renamed to "test2.ear". Is there a way to reference the embedded RAR file without hard-coding the containing archive's name?

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  • real time scenario between interface/abstract class ?

    - by JavaUser
    Hi , Please give me a real time simple example for the below questions : Where to use interface rather abstract class Where to use abstract class rather interface I need code snippet for both . Which takes low memory and which performs well . Do I need to consider the design aspect also? What is the conceptual difference not the syntactical difference .

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  • coloring buttens

    - by asm_debuger
    i want to color the text inside the button how can i do that? i made that code: for(int i=0; i<10 ;i++) { arr[i]=new Button(""+i); arr[i]. arr[i].setBackground(Color.LIGHT_GRAY); p1.add(arr[i]); this.arr[i].addActionListener(this); } the buttens text color are colored in clack if i want to color the text in the button from black to blue what i need to write?

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  • Killing Mysql processes staying in sleep command.

    - by Shino88
    Hey I am connecting a MYSQL database through hibernate and i seem to have processes that are not being killed after they are finished in the session. I have called flush and close on each session but when i check the server the last processes are still there with a sleep command. This is a new problem which i am having and was not the case yesterday. Is there any way i can ensure the killng of theses processes when i am done with a session. Below is an example of one of my classes. public JSONObject check() { //creates a new session needed to add elements to a database Session session = null; //holds the result of the check in the database JSONObject check = new JSONObject(); try{ //creates a new session needed to add elements to a database SessionFactory sessionFactory = new Configuration().configure().buildSessionFactory(); session = sessionFactory.openSession(); if (justusername){ //query created to select a username from user table String hquery = "Select username from User user Where username = ? "; //query created Query query = session.createQuery(hquery); //sets the username of the query the values JSONObject contents query.setString(0, username); // executes query and adds username string variable String user = (String) query.uniqueResult(); //checks to see if result is found (null if not found) if (user == null) { //adds false to Jobject if not found check.put("indatabase", "false"); } else { check.put("indatabase", "true"); } //adds check to Jobject to say just to check username check.put("justusername", true); } else { //query created to select a username and password from user table String hquery = "Select username from User user Where username = :user and password = :pass "; Query query = session.createQuery(hquery); query.setString("user", username); query.setString("pass", password); String user = (String) query.uniqueResult(); if(user ==null) { check.put("indatabase", false); } else { check.put("indatabase", true); } check.put("justusername", false); } }catch(Exception e){ System.out.println(e.getMessage()); //logg.log(Level.WARNING, " Exception", e.getMessage()); }finally{ // Actual contact insertion will happen at this step session.flush(); session.close(); } //returns Jobject return check; }

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  • Alternatives to static variables in Android

    - by Mocha
    I am using static Arrays and HashMaps to store some values in my AppWidgetProvider class. But they are becoming null when the process dies, so the widget does not work anymore. Are there any alternatives to using static members to store data for an AppWidgetProvider in Android?

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  • Catching an exception that is nested into another exception

    - by Bernhard V
    Hi, I want to catch an exception, that is nested into another exception. I'm doing it currently this way: } catch (RemoteAccessException e) { if (e != null && e.getCause() != null && e.getCause().getCause() != null) { MyException etrp = (MyException) e.getCause().getCause(); ... } else { throw new IllegalStateException("Error at calling service 'beitragskontonrVerwalten'"); } } Is there a way to do this more efficient and elegant?

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  • Where to handle fatal exceptions

    - by Stephen Swensen
    I am considering a design where all fatal exceptions will be handled using a custom UncaughtExceptionHandler in a Swing application. This will include unanticipated RuntimeExceptions but also custom exceptions which are thrown when critical resources are unavailable or otherwise fail (e.g. a settings file not found, or a server communication error). The UncaughtExceptionHandler will do different things depending on the specific custom exception (and one thing for all the unanticipated), but in all cases the application will show the user an error message and exit. The alternative would be to keep the UncaughtExceptionHandler for all unanticipated exceptions, but handle all other fatal scenarios close to their origin. Is the design I'm considering sound, or should I use the alternative?

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  • How to sort an array or ArrayList<Point> ASC first by x and then by y?

    - by newba
    Hi everyone, I just want to use Collections.sort or Arrays.sort to sort a list of points (class Point) by x first and then by y. I have a class Ponto that implements Comparable like this: public int compareTo(Ponto obj) { Ponto tmp = obj; if (this.x < tmp.x) { return -1; } else if (this.x > tmp.x) { return 1; } return 0; } but now I want to sort by y too after x. How can I do that by modifying the above code? Or is that a better and "clean" way to do this? I also use to pass this code to C++, in which I've created a structure called Point with a equivalent comparable method.

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  • Duplicate Prefix Error in Jsp page with Struts

    - by Cricandcric.com
    Hi, i am creating and Configuring the Struts for the first time, when I place the following Code in my jsp page <%@ taglib uri="http://struts.apache.org/tags-bean" prefix="bean"%> <%@ taglib uri="http://struts.apache.org/tags-html" prefix="html"%> <%@ taglib uri="http://struts.apache.org/tags-logic" prefix="logic"%> <%@ taglib uri="http://struts.apache.org/tags-tiles" prefix="tiles"%> I am getting the error when i move the mouse over the 1st Line "Duplicate Prefix "html" When I move the mouse over the 2nd Line, I am getting as "Duplicate Prefix "html" Similarly for 3rd and 4th Line, Can any one tell me why is this error all about Thanks in advance

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  • Ready to use TSP library

    - by Max
    Hi, I'm currently doing a project that requires some fast TSP solving (about 50-100 nodes in 2 seconds). There are a lots of approximation algorithms out there, but I don't have time nor will to analyze them and code them myself. Are there any free libraries that can solve TSP problem (approximation will do too)? Something like sortedNodes = solveTspPrettyPlease(nodes, 2sec) would be just great. Thanks in advance.

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  • Problem with 2 levels of inheritance in hibernate mapping

    - by Seth
    Here's my class structure: class A class B extends A class C extends A class D extends C class E extends C And here are my mappings (class bodies omitted for brevity): Class A: @Entity @Inheritance(strategy=InheritanceType.SINGLE_TABLE) @MappedSuperclass @DiscriminatorColumn( name="className", discriminatorType=DiscriminatorType.STRING ) @ForceDiscriminator public abstract class A Class B: @Entity @DiscriminatorValue("B") public class B extends A Class C: @Entity @DiscriminatorValue("C") @MappedSuperclass @DiscriminatorColumn( name="cType", discriminatorType=DiscriminatorType.STRING ) @ForceDiscriminator public abstract class C extends A Class D: @Entity @DiscriminatorValue("D") public class D extends C Class E: @Entity @DiscriminatorValue("E") public class E extends C I've got a class F that contains a set of A: @Entity public class F { ... @OneToMany(fetch=FetchType.LAZY, cascade=CascadeType.ALL) @JoinTable( name="F_A", joinColumns = @JoinColumn(name="A_ID"), inverseJoinColumns = @JoinColumn(name="F_ID") ) private Set<A> aSet = new HashSet<A>(); ... The problem is that whenever I add a new E instance to aSet and then call session.saveOrUpdate(fInstance), hibernate saves with "A" as the discrimiator string. When I try to access the aSet in the F instance, I get the following exception (full stacktrace ommitted for brevity): org.hibernate.InstantiationException: Cannot instantiate abstract class or interface: path.to.class.A Am I mapping the classes incorrectly? How am I supposed to map multiple levels of inheritance? Thanks for the help!

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  • regex for matching strings that have illegal filename characters.

    - by cchampion
    I been trying to figure out how this blasted regex for two hours!!! It's midnight I gotta figure this out and go to bed!!! String str = new String("filename\\"); if(str.matches(".*[?/<>|*:\"{\\}].*")) { System.out.println("match"); }else { System.out.println("no match"); } ".*[?/<>|*:\"{\\}].*" is my regex expression. It catches everything correctly except the backslash!!! I need to know how to make it catch the backslash correctly please help! FYI, the illegal characters i'm trying to catch are ? \ / < | * : " I've got it working exception for the backslash

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  • Use PermGen space or roll-my-own intern method?

    - by Adamski
    I am writing a Codec to process messages sent over TCP using a bespoke wire protocol. During the decode process I create a number of Strings, BigDecimals and dates. The client-server access patterns mean that it is common for the client to issue a request and then decode thousands of response messages, which results in a large number of duplicate Strings, BigDecimals, etc. Therefore I have created an InternPool<T> class allowing me to intern each class of object. Internally, the pool uses a WeakHashMap<T, WeakReferemce<T>>. For example: InternPool<BigDecimal> pool = new InternPool<BigDecimal>(); ... // Read BigDecimal from in buffer and then intern. BigDecimal quantity = pool.intern(readBigDecimal(in)); My question: I am using InternPool for BigDecimal but should I consider also using it for String instead of String's intern() method, which I believe uses PermGen space? What is the advantage of using PermGen space?

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  • problem to create session of facebook

    - by khoyendra
    try { HttpClient http = new HttpClient(); http.setParams(new HttpClientParams()); //http.getHostConfiguration().setHost("http://www.facebook.com/"); http.setState(new HttpState()); String api_key = "xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx"; String secret = "xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx"; // String appId=124812364218050; //http://www.facebook.com/developers/editapp.php?app_id=124812364218050 FacebookRestClient client = new FacebookRestClient(api_key, secret); client.setIsDesktop(true); // String sessionKey = request.getParameter(FacebookParam.SESSION_KEY.toString()); // boolean b = client.users_setStatus("This is a test..."); // System.out.println("User Status RESULT : " + b); String token = client.auth_createToken(); final String loginId = "http://www.facebook.com/login.php"; GetMethod get = new GetMethod(loginId + "?api_key=" + api_key + "&v=1.0&auth_token=" +token); System.out.println("Get="+get); http.executeMethod(get); PostMethod post = new PostMethod(loginId); post.addParameter(new NameValuePair("api_key", api_key)); post.addParameter(new NameValuePair("v", "1.0")); post.addParameter(new NameValuePair("auth_token", token)); post.addParameter(new NameValuePair("fbconnect","true")); post.addParameter(new NameValuePair("return_session","true")); post.addParameter(new NameValuePair("session_key_only","true")); post.addParameter(new NameValuePair("req_perms","read_stream,publish_stream")); post.addParameter(new NameValuePair("email", email)); post.addParameter(new NameValuePair("pass", password)); System.out.println("Token ="+token); int postStatus = http.executeMethod(post); System.out.println("Response : " + postStatus); session = client.auth_getSession(token); // Here I am getting error System.out.println("Session string: " + session); long userid = client.users_getLoggedInUser(); System.out.println("User Id is : " + userid); } catch (Exception e) { e.printStackTrace(); } please solve my problem i cannot create session of facebook.

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  • How can you tell if an activity is starting or resuming?

    - by Joren
    I have an activity which pulls some JSON from my server, and then uses it to draw a list. That list launches further activities. My problem is that I can't figure out a way to tell if the activity is still alive when you go back to it, so I end up re-querying my JSON from the server and redrawing the list every time the user goes back to the activity. How can I tell if my activity is still alive so I can skip the redraw? Using onRestart works for hitting the home key then going back, but onCreate not onRestart is called if I selected a list item then hit back.

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  • Going "behind Hibernate's back" to update foreign key values without an associated entity

    - by Alex Cruise
    Updated: I wound up "solving" the problem by doing the opposite! I now have the entity reference field set as read-only (insertable=false updatable=false), and the foreign key field read-write. This means I need to take special care when saving new entities, but on querying, the entity properties get resolved for me. I have a bidirectional one-to-many association in my domain model, where I'm using JPA annotations and Hibernate as the persistence provider. It's pretty much your bog-standard parent/child configuration, with one difference being that I want to expose the parent's foreign key as a separate property of the child alongside the reference to a parent instance, like so: @Entity public class Child { @Id @GeneratedValue Long id; @Column(name="parent_id", insertable=false, updatable=false) private Long parentId; @ManyToOne(cascade=CascadeType.ALL) @JoinColumn(name="parent_id") private Parent parent; private long timestamp; } @Entity public class Parent { @Id @GeneratedValue Long id; @OrderBy("timestamp") @OneToMany(mappedBy="parent", cascade=CascadeType.ALL, fetch=FetchType.LAZY) private List<Child> children; } This works just fine most of the time, but there are many (legacy) cases when I'd like to put an invalid value in the parent_id column without having to create a bogus Parent first. Unfortunately, Hibernate won't save values assigned to the parentId field due to insertable=false, updatable=false, which it requires when the same column is mapped to multiple properties. Is there any nice way to "go behind Hibernate's back" and sneak values into that field without having to drop down to JDBC or implement an interceptor? Thanks!

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  • Add a listener inside or outside get method

    - by James P.
    I'm learning Swing and have composed an interface using a series of get methods to add components. Is it a good practise to add a Listener inside a get method as follows? I'd like to make things as decoupled as possible. private JButton getConnectButton() { if (connectButton == null) { connectButton = new JButton(); connectButton.setText("Connect"); connectButton.setSize(new Dimension(81, 16)); connectButton.setLocation(new Point(410, 5)); connectButton.addActionListener(new ActionListener() { public void actionPerformed(ActionEvent e) { // actionPerformed code goes here } }); } return connectButton; }

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  • JSP template inheritance

    - by Ryan
    Coming from a background in Django, I often use "template inheritance", where multiple templates inherit from a common base. Is there an easy way to do this in JSP? If not, is there an alternative to JSP that does this (besides Django on Jython that is :) base template <html> <body> {% block content %} {% endblock %} </body> <html> basic content {% extends "base template" %} {% block content %} <h1>{{ content.title }} <-- Fills in a variable</h1> {{ content.body }} <-- Fills in another variable {% endblock %} Will render as follows (assuming that conten.title is "Insert Title Here", and content.body is "Insert Body Here") <html> <body> <h1>Insert title Here <-- Fills in a variable</h1> Insert Body Here <-- Fills in another variable </body> <html>

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  • Encountering NullPointerException when trying to add polynoms

    - by Ayler Cruz
    I need to add two polynomials, which is composed of two ints. For example, the coefficient and the exponent 3x^2 would be constructed using 3 and 2 as parameters. I am getting a NullPointerException but I can't figure out why. Any help would be appreciated! public class Polynomial { private Node poly; public Polynomial() { } private Polynomial(Node p) { poly = p; } private class Term { int coefficient; int exponent; private Term(int coefficient, int exponent) { this.coefficient = coefficient; this.exponent = exponent; } } private class Node { private Term data; private Node next; private Node(Term data, Node next) { this.data = data; this.next = next; } } public void addTerm(int coeff, int exp) { Node pointer = poly; if (pointer.next == null) { poly.next = new Node(new Term(coeff, exp), null); } else { while (pointer.next != null) { if (pointer.next.data.exponent < exp) { Node temp = new Node(new Term(coeff, exp), pointer.next.next); pointer.next = temp; return; } pointer = pointer.next; } pointer.next = new Node(new Term(coeff, exp), null); } } public Polynomial polyAdd(Polynomial p) { return new Polynomial(polyAdd(this.poly, p.poly)); } private Node polyAdd(Node p1, Node p2) { if (p1 == p2) { Term adding = new Term(p1.data.coefficient + p2.data.coefficient, p1.data.exponent); p1 = p1.next; p2 = p2.next; return new Node(adding, null); } if (p1.data.exponent > p2.data.exponent) { p2 = p2.next; } if (p1.data.exponent < p2.data.exponent) { p1 = p1.next; } if (p1.next != null && p2.next != null) { return polyAdd(p1, p2); } return new Node(null, null); } }

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  • JList with custom renderer

    - by AhmadAssaf
    Hello, I have a JList that shows multiple JPanels on them , i have created a custom renderer that returns a new JPanel. The JPanels are displayed in the JList but they are not accessible, i cant select them and if i have a button or a text area in it i can not press it. I want to try if this works in a JList because i want to do further pagination. I managed to get it work by adding panels to a Jscroll pane, but would love to make the JList thing work. Thanks

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