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  • Help with enums in Java

    - by devoured elysium
    Is it possible to have an enum change its value (from inside itself)? Maybe it's easier to understand what I mean with code: enum Rate { VeryBad(1), Bad(2), Average(3), Good(4), Excellent(5); private int rate; private Rate(int rate) { this.rate = rate; } public void increateRating() { //is it possible to make the enum variable increase? //this is, if right now this enum has as value Average, after calling this //method to have it change to Good? } } This is want I wanna achieve: Rate rate = Rate.Average; System.out.println(rate); //prints Average; rate.increaseRating(); System.out.println(rate); //prints Good Thanks

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  • Java Multi threading - Avoid duplicate request processing

    - by seawaves
    I have following multi threaded environment scenario - Requests are coming to a method and I want to avoid the duplicate processing of concurrent requests coming. As multiple similar requests might be waiting for being processed in blocked state. I used hashtable to keep track of processed request, but it will create memory leaks, so how should keep track of processed request and avoid the same requests to be processed which may be in blocking state.

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  • Drag and Drop and identify locations with java

    - by out_sider
    I'm trying to do something quite simple, but I'm having a hard time finding good examples on the net to what I want specifically. I'd like to somehing very similer to what it's here: Dao It's a simple game called DAO and I just need to have a background image with 16 squares (4x4) and drag and drop the images (pieces) on each square to the others. I'm developing the interface using swing and I simply want to know a good place to find tutorials for such implementations or a simple suggestion on how to do it. Thanks in advance

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  • Java Error When correct code is put together

    - by Eric
    I have a few string problems that I need to put together for a complete homework assignment. They all work correctly by themselves, but when I put them together in the main function, the last one that finds the smallest word in a string gives an error. Anyone know why? public static void main(String[] args){ Scanner sc = new Scanner(System.in); //Length of Word String word1 = sc.next(); System.out.println(word1.length()); //Evens in one string odds in the other String word2 = sc.next(); StringBuilder even = new StringBuilder(); StringBuilder odd = new StringBuilder(); for(int i = 0; i < word2.length(); i++){ if(i % 2 == 0){ even.append(word2.charAt(i)); } else{ odd.append(word2.charAt(i)); } } System.out.println(even + " " + odd); //Diminishing Suffix String word3 = sc.next(); for(int j = 0; j < word3.length(); j++){ System.out.print(word3.substring(j, word3.length()) + " "); } System.out.printf("\n"); //Letter Replacement String word4 = sc.next(); String word5 = sc.next(); String word6 = sc.next(); String word7 = word4.replace(word5, word6); System.out.println(word7); //How many times x appears in xstring String word8 = sc.next(); String word9 = sc.next(); int index = word8.indexOf(word9); int count = 0; while (index != -1) { count++; word8 = word8.substring(index + 1); index = word8.indexOf(word9); } System.out.println(count); System.out.println(); //Lexicographically smallest word String Sentence = sc.nextLine(); String[] myWords = Sentence.split(" "); int shortestLengths, shortestLocation; shortestLengths=(myWords[1]).length(); shortestLocation=1; for (int i = 1; i <myWords.length; i++) { if ((myWords[i]).length() < shortestLengths) { shortestLengths=(myWords[i]).length(); shortestLocation=i; } } System.out.println(myWords[shortestLocation]); } } Talking about the lexicographically smallest one

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  • How to exclude zero in a for loop in Java

    - by user1745508
    I'm trying to exclude the zero in this nested for loop here using != 0; but it is not doing anything. I'm trying to get the probability of each out come of 2 six sided dice when rolled. I must figure out the amount of times they are rolled first, but a die doesn't have a zero in it, so I must exclude it. I can't figure out why this doesn't work. for( die2 = 0; die2 <= 6 && die2 != 0; die2++) for( die1 = 0; die1 <= 6 && die1 != 0; die1++) System.out.println("Die 2: " + (die2 * userInputValue) + " " + "Die 1: " + (die1 * userInputValue));

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  • Java: Using multiple Threads to paint simultaniously on a JPanel

    - by user347217
    I have a JPanel on which I wish to have several threads painting "animations" on. An "animation" consists of a JLabel with an ImageIcon on it, which is being moved from one area of the screen to another area. Now, problem is - I want several such animations to be portrayed on screen by those threads mentioned. Problem is - the JPanel's "paint()" method can only be trigged by one thread at a time - causing the animations to execute serially, instead of in a parallel way. Any idea how to have several such animations on screen at the same time?

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  • How to transform huge xml files in java?

    - by fx42
    As the title says it, I have a huge xml file (GBs) <root> <keep> <stuff> ... </stuff> <morestuff> ... </morestuff> </keep> <discard> <stuff> ... </stuff> <morestuff> ... </morestuff> </discard> </root> and I'd like to transform it into a much smaller one which retains only a few of the elements. My parser should do the following: 1. Parse through the file until a relevant element starts. 2. Copy the whole relevant element (with children) to the output file. go to 1. step 1 is easy with SAX and impossible for DOM-parsers. step 2 is annoying with SAX, but easy with the DOM-Parser or XSLT. so what? - is there a neat way to combine SAX and DOM-Parser to do the task?

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  • Java-Counting occurrence of word from huge textfile

    - by Naveen
    I have a text file of size 115MB. It consists of about 20 million words. I have to use the file as a word collection, and use it to search the occurrence of each user-given words from the collection. I am using this process as a small part in my project. I need a method for finding out the number of occurrence of given words in a faster and correct manner since i may use it in iterations. I am in need of suggestion about any API that i can make use or some other way that performs the task in a quicker manner. Any recommendations are appreciated.

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  • Trying to get the associated value from an Enum at runtime in Java

    - by devoured elysium
    I want to accomplish something like the following (my interest is in the toInt() method). Is there any native way to accomplish this? If not, how can I get the integer associated with an enum value (like in C#) ? enum Rate { VeryBad(1), Bad(2), Average(3), Good(4), Excellent(5); private int rate; private Rate(int rate) { this.rate = rate; } public int toInt() { return rate; } } Thanks

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  • ArrayList to Array of Strings in java

    - by rajivpradeep
    ArrayList<String> newArray = new ArrayList<String>(); newArray = urlList.getUrl(); for( int i = 0 ; i < newArray.size();i++) { System.out.println(newArray.get(i)); } newArray.toArray(mStrings );// is this correct mStrings = newArray.toArray();// or this to convert ArrayList ot String array here for( int i = 0 ; i < mStrings.length;i++) { System.out.println(mStrings[i]); }

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  • Why does java.util.concurrent.ArrayBlockingQueue use 'while' loops instead of 'if' around calls to

    - by theFunkyEngineer
    I have been playing with my own version of this, using 'if', and all seems to be working fine. Of course this will break down horribly if signalAll() is used instead of signal(), but if only one thread at a time is notified, how can this go wrong? Their code here - check out the put() and take() methods; a simpler and more-to-the-point implementation can be seen at the top of the JavaDoc for Condition. Relevant portion of my implementation below. public Object get() { lock.lock(); try { if( items.size() < 1 ) hasItems.await(); Object poppedValue = items.getLast(); items.removeLast(); hasSpace.signal(); return poppedValue; } catch (InterruptedException e) { e.printStackTrace(); return null; } finally { lock.unlock(); } } public void put(Object item) { lock.lock(); try { if( items.size() >= capacity ) hasSpace.await(); items.addFirst(item); hasItems.signal(); return; } catch (InterruptedException e) { e.printStackTrace(); } finally { lock.unlock(); } } P.S. I know that generally, particularly in lib classes like this, one should let the exceptions percolate up.

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  • Java:How to align Jpanels

    - by John
    I have this code but it doesn't work: jPanel1.add(jLabel1); jPanel2.add(jButton1); jPanel2.add(jButton2); jPanel3.add(jPanel1,jPanel1.TOP_ALIGNMENT); jPanel3.add(jPanel2,jPanel2.BOTTOM_ALIGNMENT); setContentPane(jPanel3); pack(); Please tell me why!

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  • Code explanation in java

    - by Gandalf StormCrow
    Hello everyone, this morning I came across this code, and I have absolutely no idea what that means, can anyone explain me what do these represent, ex: public class MyClass<T> ... some bits of code then private Something<T> so; private OtherThing<T> to; private Class<T> c; Thank you

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  • Java getMethod with subclass parameter

    - by SelectricSimian
    I'm writing a library that uses reflection to find and call methods dynamically. Given just an object, a method name, and a parameter list, I need to call the given method as though the method call were explicitly written in the code. I've been using the following approach, which works in most cases: static void callMethod(Object receiver, String methodName, Object[] params) { Class<?>[] paramTypes = new Class<?>[params.length]; for (int i = 0; i < param.length; i++) { paramTypes[i] = params[i].getClass(); } receiver.getClass().getMethod(methodName, paramTypes).invoke(receiver, params); } However, when one of the parameters is a subclass of one of the supported types for the method, the reflection API throws a NoSuchMethodException. For example, if the receiver's class has testMethod(Foo) defined, the following fails: receiver.getClass().getMethod("testMethod", FooSubclass.class).invoke(receiver, new FooSubclass()); even though this works: receiver.testMethod(new FooSubclass()); How do I resolve this? If the method call is hard-coded there's no issue - the compiler just uses the overloading algorithm to pick the best applicable method to use. It doesn't work with reflection, though, which is what I need. Thanks in advance!

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  • initiliase the object in java

    - by harigm
    is it the right Way we initialise the the object? I have a Class Sample(); I want to intialise the Object in my Sample1 Class After intialisation I dont require to use the object of Sample Class. In that Case Can I initialise that object as new Sample(); instead of Sample s = new Sample(), if I am not going to use s anywhere in my Sample1 Class My question, is this a good practice to do that? will there be any after affects

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  • Java loop and increment problem

    - by user552961
    Can any one tell me what is the problem in my program? String a[],b[]; int c[] = new int[b.length]; for (int j = 0; j < a.length; j++) { for (int k = 0; k < b.length; k++) { if (b[k].equals(a[j])) { c[k]++; } else { c[k] = 0; } } } I have thousands of words stored in a HashMap. Now I want to check in every file that how many time one word occurred from allWords. Can you point out mistake in my program or give me your idea that how I can do it?

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  • Java File.isDirectory() returns False for a Directory in Linux

    - by shelt536
    Please see code snippet: File[] additionalFiles = new File(FILE_PATH).listFiles(); boolean isDirectory = file.isDirectory(); I have verified that the directory path is correct, and when I run the code on Windows, the value of isDirectory is true (as it should be). Any suggestions as to why this occurs on Linux (RedHat Enterprise Linux)?

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  • Java nullPointerException with getter and setters on an object

    - by 12345
    I'm getting a nullPointerException below. Can someone explain why? Thanks! private SpatialPooler spatialPooler; private Region region; private Column column33; public void setUp() { this.spatialPooler = new SpatialPooler(); this.region = new Region(30, 40, 6, 8, 1.0f, 1, 1); this.column33 = this.region.getColumn(3, 3); } public void addActiveColumn(Column activeColumn) { this.activeColumns.add(activeColumn); // nullPointerException here! } public Column getActiveColumn(int x, int y) { for (Column activeColumn : this.activeColumns) { if (activeColumn.getX() == x && activeColumn.getY() == y) { return activeColumn; } } return null; } // in a test class that is in the same package. public void testGetAndAddActiveColumn() { this.spatialPooler.addActiveColumn(this.column33); assertNull(this.spatialPooler.getActiveColumn(3, 3)); this.column33.setActiveState(true); assertEquals(this.column33, this.spatialPooler.getActiveColumn(3, 3)); }

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  • Problem decrementing in Java with '-='

    - by hanesjw
    I'm making a scrolling game on Android and am having a hard time figuring out why the code below does not decrement past 0. Objects start at the end of the screen (so the x position is equal to the width of the screen) the objects move accross the screen by decrementing their x positions. I want them to scroll off of the screen, but when the x position hits 0, the objects just stay at 0, they do not move into the negatives. Here is my code to move objects on the screen private void incrementPositions(long delta) { float incrementor = (delta / 1000F) * Globals.MAP_SECTION_SPEED; for(Map.Entry<Integer, HashMap<Integer, MapSection>> column : scrollingMap.entrySet()) { for(Map.Entry<Integer, MapSection> row : column.getValue().entrySet()) { MapSection section = row.getValue(); section.x -= incrementor; } } } It works ok if I change section.x -= incrementor; to section.x = section.x - (int)incrementor; but if i do that the scrolling doesn't appear as smooth.

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