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  • Get the key and value of Map that is used Inside another Map (JAVA)

    - by Umair Iqbal
    I am using a map inside another map, The key of the outer map is Integer and the value is another Map. I get the values as expected but I don't know how to get the key and value of teh inner map. Here is the code Map<Integer, Map<Integer, Integer>> cellsMap = new HashMap<Integer, Map<Integer, Integer>>(); Map<Integer , Integer> bandForCell = cellsMap.get(band_number); if (bandForCell == null) bandForCell = new HashMap<Integer, Integer>(); bandForCell.put(erfcn, cell_found); cellsMap.put(band_number, bandForCell); csv.writeCells((Map<Integer, Map<Integer, Integer>>) cellsMap); public void writeCells (Map<Integer, Map<Integer, Integer>> cellsMap ) throws IOException { for (Map.Entry<Integer, Map<Integer, Integer>> entry : cellsMap.entrySet()) { System.out.println("Key: " + entry.getKey() + ". Value: " + entry.getValue() + "\n"); } } Out put of my Map Key: 20 Value: {6331=0, 6330=1, 6329=1, 6328=0, 6335=1, 6437=0, 6436=1} The value in the above output is another map. How can I get the key and value of the inner map from the value of the outer map? Like Keys of inner map = 6331, 6330, 6329 .... and values of inner map = 0 , 1 , 1 , 0 ... Thanks

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  • Close resources before exiting JFrame and TCP communication in Java

    - by Oz Molaim
    1. I'm writing a chat based application on TCP communication. I'm using NetBeans and I want to add functionality to the default EXIT_ON_CLOSE when exiting JFrame. The reason of course is because I want to clean resources and end threads safely. How can I call a method that clear resources and only then close the JFrame safely and end the process. 2. I need to implement the server side. The server has List/HashMap/Queue of 'Socket' with their chat nick-names. Is there any simple design pattern to do it correctly because I don't want to re-invent the wheel. thanks.

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  • Java variables -> replace? RAM optimization

    - by poeschlorn
    Hi guys, I just wanted to know what happens behind my program when I declare and initialize a variable and later initialize it again with other values, e.g. an ArrayList or something similar. What happens in my RAM, when I say e.g. this: ArrayList<String> al = new ArrayList<String>(); ...add values, work with it and so on.... al = new ArrayList<String>(); So is my first ArrayList held in RAM or will the second ArrayList be stored on the same position where the first one has been before? Or will it just change the reference of "al"? If it is not replaced...is there a way to manually free the RAM which was occupied by the first arraylist? (without waiting for the garbage collector) Would it help to set it first =null? Nice greetings, poeschlorn

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  • [Java] Implement a RSA algorithm

    - by Robin Monjo
    Hello everyone. I want to implement a RSA algorithm to encrypt an image (byte[]). To generate my two keys I used this piece of code : KeyPairGenerator keygen = KeyPairGenerator.getInstance("RSA"); keygen.initialize(512); keyPair = keygen.generateKeyPair(); Once public and private key are generated, I would like to show them to the user so he can distribute the public key and use the private key to decode. How can I get back those key ? Using keygen.getPrivateKey() and keygen.getPublicKey() give me all the information of the RSA algorithm, not only the keys I need. Thanks

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  • Java KeyListener in separate class

    - by Chris
    So I have my main class here, where basically creates a new jframe and adds a world object to it. The world object is basically where all drawing and keylistening would take place... public class Blobs extends JFrame{ public Blobs() { super("Blobs :) - By Chris Tanaka"); setVisible(true); setResizable(false); setSize(1000, 1000); setIgnoreRepaint(true); setDefaultCloseOperation(EXIT_ON_CLOSE); add(new World()); } public static void main(String[] args) { new Blobs(); } } How exactly would you get key input from the world class? (So far I have my world class extending a jpanel and implementing a keylistener. In the constructor i addKeyListener(this). I also have these methods since they are auto implemented: public void keyPressed(KeyEvent e) { if (e.getKeyCode() == KeyEvent.VK_W) System.out.println("Hi"); } public void keyReleased(KeyEvent e) {} public void keyTyped(KeyEvent e) {} However this does not seem to work?

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  • Java threadpool functionality

    - by cpf
    Hi stackoverflow, I need to make a program with a limited amount of threads (currently using newFixedThreadPool) but I have the problem that all threads get created from start, filling up memory at alarming rate. I wish to prevent this. Threads should only be created shortly before they are executed. e.g.: I call the program and instruct it to use 2 threads in the pool. The program should create & launch the first 2 Threads immediately (obviously), create the next 2 to wait for the previous 2, and at that point wait until one or both of the first 2 ended executing. I thought about extending executor or FixedThreadPool or such. However I have no clue on how to start there and doubt it is the best solution. Easiest would have my main Thread sleeping on intervals, which is not really good either... Thanks in advance!

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  • Second level cache for java web app and its alternatives

    - by EugeneP
    Between the transitions of the web app I use a Session object to save my objects in. I've heard there's a program called memcached but there's no compiled version of it on the site, besides some people think there are real disadvantages of it. Now I wanna ask you. What are alternatives, pros and cons of different approaches? Is memcached painpul for sysadmins to install? Is it difficult to embed it to the existing infrastructure from the perspective of a sysadmin? What about using a database to hold temporary data between web app transitions? Is it a normal practice?

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  • Question about layout in java.

    - by extro
    I have two panels main_panel and child_panel. I have set layout for main_panel by using "main_panel.setLayout(flowlayout)" and added child_panel in main_panel by using "main_panel.add(child_panel)". This child_panel gets added to main_panel but its position is at the cross-section of horizontal midpoint and top vertical section of screen. But I want child_panel to be at the top left corner, something I could have done by using "child_panel.setlocation(a,b)" method, if I have set the Layout of main_panel as NULL. I have used flowlayout here because I want components in the JPanel to keep adjusting with the size of JFrame. So question is, can I add child_panel to main_panel at the exact location I want, even if I set the Layout of main_panel as not NULL.

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  • Are there any other Java schedulers besides Quartz(FOSS) and Flux(Commercial)

    - by mP
    I am interested in finding out about other job scheduling packages besides Quartz and Flux. Given the plethora of web frameworks i find it perculiar that there is really only one scheduler. Are there others that perhaps are very much unknown/unpopular ? Spring Batch Not really a scheduling solution but rather a batch job coordinator etc. http://static.springsource.org/spring-batch/faq.html#schedulers How does Spring Batch differ from Quartz? Is there a place for them both in a solution? Spring Batch and Quartz have different goals. Spring Batch provides functionality for processing large volumes of data and Quartz provides functionality for scheduling tasks. So Quartz could complement Spring Batch, but are not excluding technologies. A common combination would be to use Quartz as a trigger for a Spring Batch job using a Cron expression and the Spring Core convenience SchedulerFactoryBean .

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  • Problem loading java properties

    - by markovuksanovic
    I am trying to load properties from a file (test.properties) The code I use is as follows: URL url = getClass().getResource("../resources/test.properties"); properties.load(url.openStream()); But when executing the second line I get a NPE. (null pointer exception) I'm not sure what's wrong here... I have checked that the file exists at the location where URL points to... Any help is appreciated....

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  • Java: Set<E> collection, where items are identified by its class

    - by mschayna
    I need Set collection, where its items will be identified by items class. Something like ReferenceIdentityMap from Appache Collections, but on class scope i.e. two different instances of same class must be identified as same in this collection. You know, it is a violation of equals()/hashCode() identity principle but in occasional use it makes sense. I have done this in simple class backing with Map<Class<? extends E>, E>, but due to simplicity it doesn't implement Set<E>. There may be a more elegant solution, decorator of any Set<E> would be great. Is there any implementation of such collection there (Apache/Google/something/... Collections)?

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  • String replaceAll method (Java)

    - by Mr CooL
    I have following problem, Code: String a="Yeahh, I have no a idea what's happening now!"; System.out.println(a); a=a.replaceAll("a", ""); System.out.println(a); Before removing 'a', result: Yeahh, I have no a idea what's happening now! Actual Result: After removing 'a', result: Yehh, I hve no ide wht's hppening now! Desired Result: Yeahh, I have no idea what's happening now! Anyone can gimme some advices to achieve my desired result?

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  • java - powermock whenNew doesnt seem to work, calls the actual constructor

    - by user1331243
    I have two final classes that are used in my unit test. I am trying to use whenNew on the constructor of a final class, but I see that it calls the actual constructor. The code is @PrepareForTest({A.class, B.class, Provider.class}) @Test public void testGetStatus() throws Exception { B b = mock(B.class); when(b.getStatus()).thenReturn(1); whenNew(B.class).withArguments(anyString()).thenReturn(b); Provider p = new Provider(); int val = p.getStatus(); assertTrue((val == 1)); } public class Provider { public int getStatus() { B b = new B("test"); return b.getStatus(); } } public final class A { private void init() { // ...do soemthing } private static A a; private A() { } public static A getInstance() { if (a == null) { a = new A(); a.init(); } return a; } } public final class B { public B() { } public B(String s) { this(A.getInstance(), s); } public B(A a, String s) { } public int getStatus() { return 0; } } On debug, I find that its the actual class B instance created and not the mock instance that is returned for new usage and assertion fails. Any pointers on how to get this working. Thanks

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  • Mix of Arabic and English causes problems in JTextArea (Java)

    - by Dan
    I have a JTextArea which displays HTML of an Arabic web page. So it's essentially a mix of English and Arabic. In the JTextArea, with columns set to 30, certain text just disappears instead of wrapping properly. The weird thing is that if I copy the invisible text and paste it into Notepad, then I can see it in Notepad. If I change the number of columns to 40, everything displays fine. Any ideas?

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  • Extracting Mail from Microsoft Exchange server 2007 through IMAPS in java

    - by abhishekgem84
    props.put("mail.debug", "true"); props.setProperty("mail.store.protocol","imaps"); props.setProperty("mail.imaps.auth.plain.disable","false"); props.setProperty("mail.imaps.host","Mail3.connect.com"); props.setProperty("mail.imaps.port","135"); props.setProperty("mail.imaps.user","test"); props.setProperty("mail.imaps.pwd","123"); props.setProperty("mail.imaps.ssl.protocols","SSL"); props.setProperty("mail.imaps.socketFactory.class", "javax.net.ssl.SSLSocketFactory"); props.setProperty("mail.imaps.socketFactory.fallback", "false"); props.setProperty("mail.imaps.socketFactory.port", "135"); i have done all this but it still says javax.mail.AuthenticationFailedException: failed to connect, no password specified? kindly help me out thanks

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  • java applet - javascript communication

    - by udhaya
    Applet Communication: write a small applet and embed it in html-file with following functionality. 1. change applet bg color by receiving a javascript command with the color parameter. 2. show dynamic mouse position in applet-window and display position in html-site. use live-connect between applet and browser communication.

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  • Java - SwingWorker - problem in done() method

    - by Yatendra Goel
    I am using javax.swing.SwingWorker for the first time. I want to update a JLabel from the interim result published by the swing worker as follows: publish("Published String"); Now to update the JLabel, I have coded the following: process(List<String> chunks) { if (chunks.size() > 0) { String text = chunks.get(chunks.size() - 1); label.setText(text); } } The above code works but my problem(or to be more specific, my doubt) is as follows: The above swing worker task is an annonymous inner class so it can access label field. But what if I want to make the swing worker class a non-inner class. Should I need to pass label as an argument to the constructor of swing worker class so that the process() method can access. Or Is there any other way? What approach does other developer follow to update UI components from the swing worker class' result when the swing worker class is not an inner class?

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  • Loading data in constructors and not in constructors [JAVA]

    - by Richeve S. Bebedor
    i just want to know the difference between loading the data inside the constructor and loading the data outside the constructor but not inside any methods example: Loading inside constructor public class Model{ Object testobject; public Model(){ testobject=new Object(); } } VS example: Loading outside constructor public class Model{ Object testobject=new Object(); public Model(){ } }

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  • Java JEditorPane

    - by ikurtz
    ChatGUI im using 2 JEditorPane to transfer text from one to another. once i have transfered the data i do the following: JEditorPane.setText(null); JEditorPane.setCaretPosition(0); but as you can see from the attached image the return action makes the prompt appear a row down. how can i fix this?

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  • Java/swing: console component?

    - by Jason S
    I am looking for a component I can use in Swing that acts as a GUI console which has a text area with scrollbars that can be set to a particular font has an InputStream and an OutputStream that a host application can obtain accepts keyboard input, prints it onto the end of the console text, and sends that input to the InputStream prints the OutputStream text to the end of the console has some kind of FIFO-ish property whereby the amount of text displayed in the console can be limited by automatically discarding the oldest text, when appropriate allows copy (but not cut or paste or any other editing) of the console text to the system clipboard This is kind of like the Console tab in Eclipse. Are there any good libraries that provide this?

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  • Java style FOR loop in a clojure interpeter ?

    - by Kevin
    I have a basic interpreter in clojure. Now i need to implement for (initialisation; finish-test; loop-update) { statements } inside my interpreter. I will attach my interpreter code I got so far. Any help is appreciated. Interpreter (declare interpret make-env) ;; (def do-trace false) ;; ;; simple utilities (def third ; return third item in a list (fn [a-list] (second (rest a-list)))) (def fourth ; return fourth item in a list (fn [a-list] (third (rest a-list)))) (def run ; make it easy to test the interpreter (fn [e] (println "Processing: " e) (println "=> " (interpret e (make-env))))) ;; for the environment (def make-env (fn [] '())) (def add-var (fn [env var val] (cons (list var val) env))) (def lookup-var (fn [env var] (cond (empty? env) 'error (= (first (first env)) var) (second (first env)) :else (lookup-var (rest env) var)))) ;; -- define numbers (def is-number? (fn [expn] (number? expn))) (def interpret-number (fn [expn env] expn)) ;; -- define symbols (def is-symbol? (fn [expn] (symbol? expn))) (def interpret-symbol (fn [expn env] (lookup-var env expn))) ;; -- define boolean (def is-boolean? (fn [expn] (or (= expn 'true) (= expn 'false)))) (def interpret-boolean (fn [expn env] expn)) ;; -- define functions (def is-function? (fn [expn] (and (list? expn) (= 3 (count expn)) (= 'lambda (first expn))))) (def interpret-function (fn [expn env] expn)) ;; -- define addition (def is-plus? (fn [expn] (and (list? expn) (= 3 (count expn)) (= '+ (first expn))))) (def interpret-plus (fn [expn env] (+ (interpret (second expn) env) (interpret (third expn) env)))) ;; -- define subtraction (def is-minus? (fn [expn] (and (list? expn) (= 3 (count expn)) (= '- (first expn))))) (def interpret-minus (fn [expn env] (- (interpret (second expn) env) (interpret (third expn) env)))) ;; -- define multiplication (def is-times? (fn [expn] (and (list? expn) (= 3 (count expn)) (= '* (first expn))))) (def interpret-times (fn [expn env] (* (interpret (second expn) env) (interpret (third expn) env)))) ;; -- define division (def is-divides? (fn [expn] (and (list? expn) (= 3 (count expn)) (= '/ (first expn))))) (def interpret-divides (fn [expn env] (/ (interpret (second expn) env) (interpret (third expn) env)))) ;; -- define equals test (def is-equals? (fn [expn] (and (list? expn) (= 3 (count expn)) (= '= (first expn))))) (def interpret-equals (fn [expn env] (= (interpret (second expn) env) (interpret (third expn) env)))) ;; -- define greater-than test (def is-greater-than? (fn [expn] (and (list? expn) (= 3 (count expn)) (= '> (first expn))))) (def interpret-greater-than (fn [expn env] (> (interpret (second expn) env) (interpret (third expn) env)))) ;; -- define not (def is-not? (fn [expn] (and (list? expn) (= 2 (count expn)) (= 'not (first expn))))) (def interpret-not (fn [expn env] (not (interpret (second expn) env)))) ;; -- define or (def is-or? (fn [expn] (and (list? expn) (= 3 (count expn)) (= 'or (first expn))))) (def interpret-or (fn [expn env] (or (interpret (second expn) env) (interpret (third expn) env)))) ;; -- define and (def is-and? (fn [expn] (and (list? expn) (= 3 (count expn)) (= 'and (first expn))))) (def interpret-and (fn [expn env] (and (interpret (second expn) env) (interpret (third expn) env)))) ;; -- define with (def is-with? (fn [expn] (and (list? expn) (= 3 (count expn)) (= 'with (first expn))))) (def interpret-with (fn [expn env] (interpret (third expn) (add-var env (first (second expn)) (interpret (second (second expn)) env))))) ;; -- define if (def is-if? (fn [expn] (and (list? expn) (= 4 (count expn)) (= 'if (first expn))))) (def interpret-if (fn [expn env] (cond (interpret (second expn) env) (interpret (third expn) env) :else (interpret (fourth expn) env)))) ;; -- define function-application (def is-function-application? (fn [expn env] (and (list? expn) (= 2 (count expn)) (is-function? (interpret (first expn) env))))) (def interpret-function-application (fn [expn env] (let [function (interpret (first expn) env)] (interpret (third function) (add-var env (first (second function)) (interpret (second expn) env)))))) ;; the interpreter itself (def interpret (fn [expn env] (cond do-trace (println "Interpret is processing: " expn)) (cond ; basic values (is-number? expn) (interpret-number expn env) (is-symbol? expn) (interpret-symbol expn env) (is-boolean? expn) (interpret-boolean expn env) (is-function? expn) (interpret-function expn env) ; built-in functions (is-plus? expn) (interpret-plus expn env) (is-minus? expn) (interpret-minus expn env) (is-times? expn) (interpret-times expn env) (is-divides? expn) (interpret-divides expn env) (is-equals? expn) (interpret-equals expn env) (is-greater-than? expn) (interpret-greater-than expn env) (is-not? expn) (interpret-not expn env) (is-or? expn) (interpret-or expn env) (is-and? expn) (interpret-and expn env) ; special syntax (is-with? expn) (interpret-with expn env) (is-if? expn) (interpret-if expn env) ; functions (is-function-application? expn env) (interpret-function-application expn env) :else 'error)))

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