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• Java App Engine - ranked counter

  - by Richard

  I understand the sharded counter, here: http://code.google.com/appengine/articles/sharding_counters.html The problem is that a simple counter will not work in my application. I am sorting my entities by a particular variable so I am returned not so much a count, but more of a rank. My current method is: SELECT COUNT(this) FROM Entity.class WHERE value <= ? Result + 1 is then the rank of the parameter in relation to the value variable in the persistent Entity objects. The limitation of this is the highest rank being returned is 1001 because count() can give a maximum of 1000. The reason I cannot store the rank on the Entity object is that the ranks are updated very often, and re-setting this rank variable would be much too costly. Any ideas on the best way to accomplish this?

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• Java - Regex problem

  - by Yatendra Goel

  I want a regex to find the following types of strings: http://anything.abc.tld http://anything.abc.tld/ where abc - abc always remains abc anything - it could be any string tld - it could be any tld (top-level-domain) like .com .net .co.in .co.uk etc.

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• Java repaint is slow under certain conditions.

  - by Gabriel A. Zorrilla

  I'm doing a simple grid which each square is highlighted by the cursor: They are a couple of JPanels, mapgrid and overlay inside a JLayeredPane, with mapgrid on the bottom. Mapgrid just draws on initialization the grid, its paint metodh is: public void paintComponent(Graphics g) { super.paintComponent(g); Graphics2D g2d = (Graphics2D) g; g2d.setRenderingHint(RenderingHints.KEY_ANTIALIASING, RenderingHints.VALUE_ANTIALIAS_ON); for (int i = 0; i < h; i++) { for (int j = 0; j < w; j++) { g2d.setColor(new Color(128, 128, 128, 255)); g2d.drawRect(tileSize * j, i * tileSize, tileSize, tileSize); } } In the overlay JPanel is where the highlighting occurs, this is what is repainted when the mouse is moved: public void paintComponent(Graphics g) { super.paintComponent(g); Graphics2D g2d = (Graphics2D) g; g2d.setRenderingHint(RenderingHints.KEY_ANTIALIASING, RenderingHints.VALUE_ANTIALIAS_ON); g2d.setColor(new Color(255, 255, 128, 255)); g2d.drawRect((pointerX/tileSize)*tileSize,(pointerY/ tileSize)*tileSize, tileSize, tileSize); } I noticed that even though the base layer (mapgrid) is NOT repainted when the mouse moves, just the transparent overlay layer, the performance is lacking. If i give the overlay JPanel a background, its way faster. If i remove the mapgrid Antialiasing, its a bit faster too. I don't know why giving a background to the overlay layer (and thus, hiding the mapgrid) or disabling antialiasing in the mapgrid leads to much better performance. Is there a better way to do this? Why does this happen?

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• Java / Spring / JSP - how to output value added using ModelAndView.addObject

  - by Jon morgan

  Hi, I have the following code in my controller final ModelAndView m = new ModelAndView(); m.addObject("date", "15" ); In my view I have been able to output this by doing ${date} However how can I print it out using out.print or assign it to a new variable e.g. <% out.print( ${date} ) %> Thanks

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• Add Hexidecimal Header Info to JPEG File Using Java

  - by jboyd

  I need to add header info to a JPEG file in order to get it to work properly when shared on some websites, I've tracked down the correct info through a lot of Hex digging, but now I'm kind of stuck trying to get it into the file. I know where in the file it needs to go, and I know how long it is, my problem is that RandomAccessFile just overwrites existing data in the file and FileOutputStream appends the data to the end. I don't want either, I want to INSERT data starting at the third byte. My example code: File fileToChange = new File("someimage.jpg"); byte[] i = new byte[2]; i[0] = (byte)Integer.decode("0xcc"); i[1] = (byte)Integer.decode("0xcc"); RandomAccessFile f = new RandomAccessFile(new File("videothing.jpg"), "rw"); long aPositionWhereIWantToGo = 2; f.seek(aPositionWhereIWantToGo); // this basically reads n bytes in the file f.write((byte[])i); f.close(); So this doesn't work because it overwrites, and does not insert, I can't find any way to just insert data into a file

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• Java - Get a list of all Classes loaded in the JVM

  - by Walter White

  Hi all, I would like to get a list of all the classes loaded in the JVM at a particular point in time. The classes are in a particular package and are accessible via /WEB-INF/classes and not through a jar file in /WEB-INF/lib. How would I get a list of classes? Would I simply get the classpath, list all the files, then look for the names? Walter

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• How do I center a java.awt.FileDialog on the screen

  - by Software Monkey

  I have never been able to figure this one out; the usual suspects don't work. Given: FileDialog dlg=null; dlg=new FileDialog(owner,"Select File to Load",FileDialog.LOAD); dlg.setFile(null); dlg.setVisible(true); is there any way to get that dialog centered?

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• Java Junit testing problem

  - by agazerboy

  Hi All, I am using Junit 4. My whole program is working fine. I am trying to write a test case. But there is one error... here is very basic sample test public class di extends TestCase{ private static Records testRec; public void testAbc() { Assert.assertTrue( "There should be some thing.", di.testRec.getEmployee() > 0); } } and when i run this it give me error that fName can not be null if i use super and do like this public TestAgnes() { super("testAbc"); } it work all fine. It wasn't this before with JUnit 3.X am I doing wrong or they changed it :( Sorry if I am not clear Is there any way to executre test without super? or calling functions etc. ?

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• Java, LinkedList of Strings. Insert in alphabetical order

  - by user69514

  I have a simple linked list. The node contains a string (value) and an int (count). In the linkedlist when I insert I need to insert the new Node in alphabetical order. If there is a node with the same value in the list, then I simply increment the count of the node. I think I got my method really screwed up. public void addToList(Node node){ //check if list is empty, if so insert at head if(count == 0 ){ head = node; head.setNext(null); count++; } else{ Node temp = head; for(int i=0; i<count; i++){ //if value is greater, insert after if(node.getItem().getValue().compareTo(temp.getItem().getValue()) > 0){ node.setNext(temp.getNext()); temp.setNext(node); } //if value is equal just increment the counter else if(node.getItem().getValue().compareTo(temp.getItem().getValue()) == 0){ temp.getItem().setCount(temp.getItem().getCount() + 1); } //else insert before else{ node.setNext(temp); } } } }

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• Taking User Input in Java

  - by jdbeverly87

  I'm creating a program that checks if a word or phrase is a palindrome. I have the actual "palindrome tester" figured out. What I'm stuck with is where and what to place in my code to have the console read out "Enter palindrome..." and then text. I've tried with IO but it doesnt work out right. Also, how do I create a loop to keep going? This code only allows one at a time `public class Palindrome { public static void main(String args[]) { String s=""; int i; int n=s.length(); String str=""; for(i=n-1;i>=0;i--) str=str+s.charAt(i); if(str.equals(s)) System.out.println(s+ " is a palindrome"); else System.out.println(s+ " is not a palindrome"); } }

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• Weird Java Math ,10 ^ 1 = 11?

  - by Simon

  For an exercise I was writing a loop that turns a string into an integer without using the built in functions by multiplying each individual value by its numerical position. 75 would be 7*(10 ^ 1) + 5*(10 ^ 0), for example. However, for some reason (10 ^ 1) keeps coming back as 11. Is there some mistake I have made or an explanation for this?

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• Write Java Method Signature with Annotated paramaters with JDT

  - by Scott

  Hi, I am writing an eclipse plug-in which generates code. I am leveraging eclipse jdt to gen out classes, fields, and methods. One of the requirements I have is to generate methods with annotated paramaters... public returnType foo(@someAnnotation int id) { ..... ..... } Does anybody know how to write out the @someAnnotation using JDT? To write out normal parameters in JDT you could do something like the following Signature.createTypeSignature("int", false)

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• Static initializer in Java

  - by Szere Dyeri

  My question is about one particular usage of static keyword. It is possible to use static keyword to cover a code block within a class which does not belong to any function. For example following code compiles: public class Test { private static final int a; static { a = 5; doSomething(a); } private static int doSomething(int x) { return (x+5); } } If you remove the static keyword it complains because the variable a is final. However it is possible to remove both final and static keywords and make it compile. It is confusing for me in both ways. How am I supposed to have a code section that does not belong to any method? How is it possible to invoke it? In general, what is the purpose of this usage? Or better, where can I find documentation about this?

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• Create a mirrored linked list in Java

  - by glacier89

  Linked-List: Mirror Consider the following private class for a node of a singly-linked list of integers: private class Node{ public int value; public Node next; } A wrapper-class, called, ListImpl, contains a pointer, called start to the first node of a linked list of Node. Write an instance-method for ListImpl with the signature: public void mirror(); That makes a reversed copy of the linked-list pointed to by start and appends that copy to the end of the list. So, for example the list: start 1 2 3 after a call to mirror, becomes: start 1 2 3 3 2 1 Note: in your answer you do not need to dene the rest of the class for ListImpl just the mirror method.

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• Java: Last access of 2D HashMap

  - by JamieFlowers

  I have the following structure: HashMap< String, HashMap< String, String Now i want to know the last accessed element in the 2nd dimension. I know there is TreeMap which makes sense in the 1rst dimension but after that it doesn't make any sense. How can I keep track of a 2D HashMap ordering? With access i mean: value = hashmap.get("a").get("1") value = hashmap.get("b").get("2") value = hashmap.get("c").get("3") hashmap.removeLast(); hashmap.removeLast(); hashmap.removeLast();

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• Java - AWT / Swing - handling the Event Descriptor Thread

  - by waitinforatrain

  Hi, I have a question about the 'Event Descriptor Thread'. I have a Main class that is also a JFrame. It initialises the rest of the components in the code, some of them do not involve Swing and some of them do. Is it enough to simply initialise the Main class using the EDT like this?... public static void main(String[] args) { javax.swing.SwingUtilities.invokeLater(new Runnable() { public void run() { new Main(); } }); } This way everything would run on the Event Dispatcher thread.

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• Specify connection timeout in java.nio

  - by miorel

  Using non-blocking I/O, the code for connecting to a remote address looks something like: SocketChannel channel = SelectorProvider.provider().openSocketChannel(); channel.configureBlocking(false); channel.connect(address); The connection process will then have to be finished by invoking finishConnect() on the channel when some selector says the corresponding key isConnectable(). Is there a way to specify the connection timeout when using this idiom?

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• Quick Java question about variables

  - by Spencer

  I'm declaring a variable: private static final String filename = "filename.txt"; First, does the order of private static final matter? If not, is there a standard excepted sequence or convention? Second, the filename in my application is fixed. Is this the best was to store it's value? Thanks, Spencer

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• loop through HashMap Java jsp

  - by blub

  Hello, the related Questions couldn't help me very much. How can i loop through a HashMap in jsp like this example: <% HashMap<String, String> countries = MainUtils.getCountries(l); %> <select name="ccountry" id="ccountry" > <% //HERE I NEED THE LOOP %> </select>*<br/>

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• how to get previous date in java

  - by Sergey

  I have a String in format yyyyMMdd. Is there a simple way to get a String with previous date in the same format? Thanks

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• Java Charset problem on linux

  - by scot

  Hi, problem: I have a string containing special characters which i convert to bytes and vice versa..the conversion works properly on windows but on linux the special character is not converted properly.the default charset on linux is UTF-8 as seen with Charset.defaultCharset.getdisplayName() however if i run on linux with option -Dfile.encoding=ISO-8859-1 it works properly.. how to make it work using the UTF-8 default charset and not setting the -D option in unix environment. edit: i use jdk1.6.13 edit:code snippet works with cs = "ISO-8859-1"; or cs="UTF-8"; on win but not in linux String x = "½"; System.out.println(x); byte[] ba = x.getBytes(Charset.forName(cs)); for (byte b : ba) { System.out.println(b); } String y = new String(ba, Charset.forName(cs)); System.out.println(y); ~regards daed

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• Java JFrame method pack() problem

  - by Oliver

  Hi, I have a frame with 4 JPanels and 1 JScrollPane, the 4 panels are in border layout north, east, south, west and the scrollpane in the center. I have been trying to get the pack method for a frame fuctioning but when run you just get the title bar of the window. Any Ideas? Thank you in advance. JFrame conFrame; JPanel panel1; JPanel panel2; JPanel panel3; JPanel panel4; JScrollPane listPane; JList list; Object namesAr[]; ... ... ... namesAr= namesA.toArray(); list = new JList(namesAr); list.setSelectionMode(ListSelectionModel.SINGLE_SELECTION); list.setLayoutOrientation(JList.HORIZONTAL_WRAP); list.setVisibleRowCount(-3); list.addListSelectionListener(this); listPane = new JScrollPane(list); panel1 = new JPanel(); panel2 = new JPanel(); panel3 = new JPanel(); panel4 = new JPanel(); conFrame.setLayout(new BorderLayout()); panel1.setPreferredSize(new Dimension(100, 100)); panel2.setPreferredSize(new Dimension(100, 100)); panel3.setPreferredSize(new Dimension(100, 100)); panel4.setPreferredSize(new Dimension(100, 100)); panel1.setBackground(Color.red); panel2.setBackground(Color.red); panel3.setBackground(Color.red); panel4.setBackground(Color.red); conFrame.pack(); conFrame.add(panel1, BorderLayout.NORTH); conFrame.add(panel2, BorderLayout.EAST); conFrame.add(panel3, BorderLayout.SOUTH); conFrame.add(panel4, BorderLayout.WEST); conFrame.add(listPane, BorderLayout.CENTER); conFrame.setVisible(true);

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• Sync between ms exchange calendar and Java app

  - by arkadiy

  Hi, we are developing a CRM app which holds customer meeting info. Users have requested that their Outlook calendars should reflect the activity they have booked in the CRM application and vice versa. Is there any solution to achieve this? Preferably not using any plugins or installs on the end user's PC?

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• Java anagram recursion List<List<String>> only storing empty lists<Strings>

  - by Riff Rafffer

  Hi In this recursion method i am trying to find all anagrams and add it to a List but what happens when i run this code is it just returns alot of empty Lists. private List<List<String>> findAnagrams(LetterInventory words, ArrayList<String> anagram, int max, Map<String, LetterInventory> smallDict, int level, List<List<String>> result) { ArrayList<String> solvedWord = new ArrayList<String>(); LetterInventory shell; LetterInventory shell2; if (level < max || max == 0) { Iterator<String> it = smallDict.keySet().iterator(); while (it.hasNext()) { String k = it.next(); shell = new LetterInventory(k); shell2 = words; if (shell2.subtract(shell) != null) { anagram.add(k); shell2 = words.subtract(shell); if (shell2.isEmpty()) { //System.out.println(anagram.toString()); it prints off fine here result.add(anagram); // but doesnt add here } else findAnagrams(shell2, anagram, max, smallDict, level + 1, result); anagram.remove(anagram.size()-1); } } } return results; }

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• Java : method to to print relative pathname?

  - by HH

  I am hesitant just to look at some env.vars and try to replace things with regexes. So is there a ready method to print relative pathnames system-independently? $ echo ~ /u/user $ pwd /u/user/OH/one/src $ echo "Like relative pathnames ~/OH/one/src, not /u/user/OH/one/src."

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