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  • Whats the best way to parse a file in Java

    - by chitresh
    Hi All, I have a text file with Tag - Value format data. I want to parse this file to form a Trie. What will be the best approach? Sample of File: (String inside "" is a tag and '#' is used to comment the line.) #Hi, this is a sample file. "abcd" = 12; "abcde" = 16; "http" = 32; "sip" = 21;

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  • Java Applet Buffering images

    - by Dan
    OK so here's my code: http://www.so.pastebin.com/Qca4ERmy I am trying to use buffers so the applet won't flicker upon redraw() but it seems I am having trouble. The applet still flickers.... Help? Thank you.

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  • Why fill() and copy() of Collections in java is implemented this way

    - by Priyank Doshi
    According to javadoc... Collections.fill() is written as below : public static <T> void fill(List<? super T> list, T obj) { int size = list.size(); if (size < FILL_THRESHOLD || list instanceof RandomAccess) { for (int i=0; i<size; i++) list.set(i, obj); } else { ListIterator<? super T> itr = list.listIterator(); for (int i=0; i<size; i++) { itr.next(); itr.set(obj); } } } Its easy to understand why they didn't use listIterator for if (size < FILL_THRESHOLD || list instanceof RandomAccess) condition as of RandomAccess. But whats the use of size < FILL_THRESHOLD in above? I mean is there any significant performance benefit over using iterator for size>=FILL_THRESHOLD and not for size < FILL_THRESHOLD ? I see the same approach for Collections.copy() also : public static <T> void copy(List<? super T> dest, List<? extends T> src) { int srcSize = src.size(); if (srcSize > dest.size()) throw new IndexOutOfBoundsException("Source does not fit in dest"); if (srcSize < COPY_THRESHOLD || (src instanceof RandomAccess && dest instanceof RandomAccess)) { for (int i=0; i<srcSize; i++) dest.set(i, src.get(i)); } else { ListIterator<? super T> di=dest.listIterator(); ListIterator<? extends T> si=src.listIterator(); for (int i=0; i<srcSize; i++) { di.next(); di.set(si.next()); } } } FYI: private static final int FILL_THRESHOLD = 25; private static final int COPY_THRESHOLD = 10;

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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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  • construct a unique number for a string in java

    - by praveen
    We have a requirement of reading/writing more than 10 million strings into a file. Also we do not want duplicates in the file. Since the strings would be flushed to a file as soon as they are read we are not maintaining it in memory. We cannot use hashcode because of collisions in the hash code due to which we might miss a string as duplicate. Two other approaches i found in my googling: 1.Use a message digest algorithm like MD5 - but it might be too costly to calculate and store. 2.Use a checksum algorithm. [i am not sure if this produces a unique key for a string- can someone please confirm] Is there any other approach avaiable. Thanks.

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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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  • 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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  • Creating Java Dialogs

    - by mike_hornbeck
    What would be the easiest way for creating a dialog: - in one window I'm giving data for envelope addressing, also set font type from list of sizes - when clicked OK, in the same window or in next window I get preview of how the envelope would look like with the given names, and used selected font size It should look similarly to this : Should I use Jdialog ? Or will JOptionPane will be enough ? The next step will be to choose color of font and background so I must keep that in mind.

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  • Java for-loop problem

    - by Dan
    OK so here's my code: http://so.pastebin.com/9swaiuRy The problem is that I am trying to make certain tiles blocked so the player cannot walk on them. However, it's only reading the FIRST tile which is board[0][0] and everything else is not checked.... What am I doing wrong? :( Thank you.

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  • Pointer-like behavior in Java

    - by Shmoo
    I got the following: class A{ int foo; } class B extends A{ public void bar(); } I got a instance of A and want to convert it to an instance of B without losing the reference to the variable foo. For example: A a = new A(); a.foo = 2; B b = a; <-- what I want to do. //use b b.foo = 3; //a.foo should now be 3 Thanks for any help!

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  • Java Sorting "queue" list based on DateTime and Z Position (part of school project)

    - by Kuchinawa
    For a school project i have a list of 50k containers that arrive on a boat. These containers need to be sorted in a list in such a way that the earliest departure DateTimes are at the top and the containers above those above them. This list then gets used for a crane that picks them up in order. I started out with 2 Collection.sort() methods: 1st one to get them in the right XYZ order Collections.sort(containers, new Comparator<ContainerData>() { @Override public int compare(ContainerData contData1, ContainerData contData2) { return positionSort(contData1.getLocation(),contData2.getLocation()); } }); Then another one to reorder the dates while keeping the position in mind: Collections.sort(containers, new Comparator<ContainerData>() { @Override public int compare(ContainerData contData1, ContainerData contData2) { int c = contData1.getLeaveDateTimeFrom().compareTo(contData2.getLeaveDateTimeFrom()); int p = positionSort2(contData1.getLocation(), contData2.getLocation()); if(p != 0) c = p; return c; } }); But i never got this method to work.. What i got working now is rather quick and dirty and takes a long time to process (50seconds for all 50k): First a sort on DateTime: Collections.sort(containers, new Comparator<ContainerData>() { @Override public int compare(ContainerData contData1, ContainerData contData2) { return contData1.getLeaveDateTimeFrom().compareTo(contData2.getLeaveDateTimeFrom()); } }); Then a correction function that bumps top containers up: containers = stackCorrection(containers); private static List<ContainerData> stackCorrection(List<ContainerData> sortedContainerList) { for(int i = 0; i < sortedContainerList.size(); i++) { ContainerData current = sortedContainerList.get(i); // 5 = Max Stack (0 index) if(current.getLocation().getZ() < 5) { //Loop through possible containers above current for(int j = 5; j > current.getLocation().getZ(); --j) { //Search for container above for(int k = i + 1; k < sortedContainerList.size(); ++k) if(sortedContainerList.get(k).getLocation().getX() == current.getLocation().getX()) { if(sortedContainerList.get(k).getLocation().getY() == current.getLocation().getY()) { if(sortedContainerList.get(k).getLocation().getZ() == j) { //Found -> move container above current sortedContainerList.add(i, sortedContainerList.remove(k)); k = sortedContainerList.size(); i++; } } } } } } return sortedContainerList; } I would like to implement this in a better/faster way. So any hints are appreciated. :)

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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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  • Sending arbitrarily long string over Java TCP socket

    - by bibismcbryde
    I have an Android app that communicates over a TCP socket with a server I wrote. The method I'm using now to read and write output works fine for smaller strings (up to 60kB) but I get an exception thrown when the string is much longer than that. Here is the relevant part of what I have for the server and client: Server: DataInputStream dis = null; DataOutputStream dos = null; try { dis = new DataInputStream(server.getInputStream()); dos = new DataOutputStream(server.getOutputStream()); String input = ""; input = dis.readUTF(); handle_input info = new handle_input(input, id); String xml = info.handle(); dos.writeUTF(xml); server.close(); } Client: Socket socket = null; DataOutputStream dos = null; DataInputStream dis = null; Boolean result; try { socket = new Socket(ip, port); dos = new DataOutputStream(socket.getOutputStream()); dis = new DataInputStream(socket.getInputStream()); dos.writeUTF(the_text); String in = ""; while (in.equals("")) { in += dis.readUTF(); } } How can I modify it to deal with potentially enormous Strings? I've been looking around and can't seem to find a clear answer. Thanks.

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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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  • 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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  • 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 Insert Help...???

    - by El Classico
    I am trying to do an Insert, Update and Delete on a table in MS Access. Everything works fine for a SELECT statement. But when doing the other three operations, I don't seem to get any errors, but the actions are not reflected on to the DB. Please help... THe INSERT statement is as follows: PreparedStatement ps = con.prepareStatement("INSERT INTO Student VALUES (?, ?, ?, ?, ?, ?, ?, ?)"); ps.setInt(1,1); ps.setString(2,"ish"); ps.setInt(3,100); ps.setInt(4,100); ps.setInt(5,100); ps.setInt(6,300); ps.setInt(7,100); ps.setString(8,"A"); ps.executeUpdate(); Also may I know why PreparedStatement is used except for SELECT statement...

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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 identify end of InputStream in java

    - by Vardhaman
    I am trying to read bytes from server using Socket program, ie I am using InputStream to read the bytes. If I pass the length size I am able to read the bytes, but I am not sure what may be the length. So I am not able initialize the byte array. Also I tried while (in.read() !=-1), I observered it loop works fine when the data is sent , but the next line after the loop is not executable , I feel its still looking for the data in the stream but there is no ata. If I close the Server connection , then my client will execute the next line followed to the loop. I am not sure where I am going wrong? this.in = socket.getInputStream(); int dataInt = this.in.read(); while(dataInt != -1){ System.out.print(","+i+"--"+dataInt); i++; dataInt = this.in.read(); } System.out.print("End Of loop"); I get the output as:- ,1--0,2--62,3--96,4--131,5--142,6--1,7--133,8--2,9--16,10--48,11--56,12--1,13--0,14--14,15--128,16--0,17--0,18--0,19--48,20--0,21--0,22--0,23--0,24--0,25--1,26--0,27--0,28--38,29--114,30--23,31--20,32--70,33--3,34--20,35--1,36--133,37--48,38--51,39--49,40--52,41--49,42--55,43--49,44--52,45--52,46--54,47--55,48--50,49--51,50--52,51--48,52--53,53--56,54--51,55--48,56--48,57--57,58--57,59--57,60--57,61--57,62--57,63--57,64--56 But no output for :- End Of loop Please guide how shall I close the loop? Looking forward for you response. Thanking you all 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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