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  • Java Hibernate Lazy=false

    - by Noor
    When setting Lazy=false, then hibernate will automatically loads the objects into the required sets e.g. <set name="Options" table="ATTRIBUTEOPTION" inverse="false" cascade="all" lazy="false"> <key> <column name="ATTRIBUTEID" /> </key> <one-to-many class="com.BiddingSystem.Models.AttributeOption" /> </set> but if in my xml mapping, I place lazy=true and in some place in my application i decide that i want to load all attribute options, should i do it manually, or is there a technique which lets tells hibernate that now i want to set lazy=false??

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  • Reference variable to an object instantiated/initialized in another class in Java

    - by Alex
    The reason I'm asking is because I'm getting NullPointerException. I now this is very easy but I'm pretty new programming and find this a bit confusing. So say I have initialized an object in a class and want to access that same object from another class. Like now for instance I'm working on a small Chess game, in my model Game class I have an instance of Board, an object. Board, in turn, has an array of Squares. Square[][]. Game has board, board has Square[][]. Now if I want to access the Square[][] through the object board (in Game) of type Board. Do I just declare a variable with the same name and type or do I have to initialize it again? Board board OR Board board = new Board(); Note, I have already initialized board in the class Game so if I do it again, won't they be two totally different Board objects?

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  • Using enums in Java across multiple classes

    - by Richard Mar.
    I have the following class: public class Card { public enum Suit { SPACES, HEARTS, DIAMONDS, CLUBS }; public Card(Suit nsuit, int nrank) { suit = nsuit; rank = nrank; } private Suit suit; private int rank; } I want to instantiate it in another class, but that class doesn't understand the Suit enum. Where should I put the enum to make it publicly visible?

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  • Declare java enum with a String array

    - by chama
    I'm trying to declare an enum type based on data that I'm retrieving from a database. I have a method that returns a string array of all the rows in the table that I want to make into an enumerated type. Is there any way to construct an enum with an array? This is what I tried, but from the way it looked in eclipse, it seemed like this just created a method by that name: public enum ConditionCodes{ Condition.getDescriptions(); } Thank you in advance!

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  • How to analyze evenness/oddness of numbers in Java

    - by appreciation
    I have to write a program which reads in 3 numbers (using input boxes), and depending on their values it should write one of these messages: All 3 numbers are odd OR All 3 numbers are even OR 2 numbers are odd and 1 is even OR 1 number is odd and 2 are even This is what I have so far: import javax.swing.JOptionPane; class program3 { public static void main(String[] args) { String num1 = JOptionPane.showInputDialog("Enter first number."); String num2 = JOptionPane.showInputDialog("Enter second number."); String num3 = JOptionPane.showInputDialog("Enter third number."); boolean newnum1 = Integer.parseInt(num1); boolean newnum2 = Integer.parseInt(num2); boolean newnum3 = Integer.parseInt(num3); } } This is where I am stuck. I am not sure how to use the MOD to display the messages. I think I have to also use an IF Statement too...But I'm not too sure. Please help! :D

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  • Java Null Pointer Exception :-(

    - by John-Michael Reed
    I've got a Null Pointer Exception in my main that just won't go away and I'm totally out of ideas. The error is on the line "Board[x][y].color = 2;" in which Board is a public, static array of piece objects that contain instance variables like the one "color" that is being set to 2 in the above statement. Pieces is not static - that is there are many different copies of pieces, each with its own data, but only one board. The array has been initialized and defined as both public Piece[][] Board = new Piece[8][8] and public static Piece[][] Board = new Piece[8][8], but no matter how I mess around with it (getting rid of static, putting the variable in another object, etc.), I can't seem to get the error to go away. Help?

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  • Revalidate and repaint - Java Swing

    - by bosra
    I have a JPanel that I am adding JLabel's to. I then want to remove all the JLabels and add some new ones. So I do the following: panel.removeAll();panel.repaint(); panel.add(new JLabel("Add something new"); panel.revalidate(); This works fine. My problem arises when I start a new thread after this like: panel.removeAll();panel.repaint(); (1)panel.add(new JLabel("Add something new"); panel.revalidate(); //new thread to start - this thread creates new JLabels that should appear under (1) firstProducer.start(); try { firstProducer.join(); } catch (InterruptedException e) { // TODO Auto-generated catch block e.printStackTrace(); } Then the output from the original JLabels is still visible. I have read that the revalidate process is a long running task and hence the firstProducer thread is getting started while the revalidation is going on and a conflict is arising. What is the best way to deal with this?

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  • Creating a 2d matrix from an array (java)

    - by anna
    I'm supposed to write a method that creates a 2d matrix from an array, for instance: ({1, 2, 3, 4}, 3) should return the matrix {{1, 2, 3}, {4}} public class Matrix { public static int[][]toM(int[] array, int a) { int[][]matrix = new int [(array.length + a- 1)/ a][a]; for (int i = 0; i < array.length; i++){ int value = array[i]; value = value++; for (int row = 0; row < (array.length + a- 1)/a; row++) { for (int col = 0; col < a; col++) { matrix[row][col]= value++; } } } return matrix; } } I'm getting [[4, 5, 6], [7, 8, 9]]?

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  • Java splitting string by custom regex match

    - by slikz
    I am completely new to regular expressions so I'm looking for a bit of help here. I am compiling under JDK 1.5 Take this line as an example that I read from standard input: ab:Some string po:bubblegum What I would like to do is split by the two characters and colon. That is, once the line is split and put into a string array, these should be the terms: ab:Some string po:bubblegum I have this regex right now: String[] split = input.split("[..:]"); This splits at the semicolon; what I would like is for it to match two characters and a semicolon, but split at the space before that starts. Is this even possible? Here is the output from the string array: ab Some String po bubblegum I've read about Pattern.compile() as well. Is this something I should be considering?

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  • Java Detect Variable Change Using PropertyChangeSupport and PropertyChangeListener

    - by Sam
    I'm trying to print out debug statements when some third party code changes a variable. For example, consider the following: public final class MysteryClass { private int secretCounter; public synchronized int getCounter() { return secretCounter; } public synchronized void incrementCounter() { secretCounter++; } } public class MyClass { public static void main(String[] args) { MysteryClass mysteryClass = new MysteryClass(); // add code here to detect calls to incrementCounter and print a debug message } I don't have the ability to change the 3rd party MysteryClass, so I thought that I could use PropertyChangeSupport and PropertyChangeListener to detect changes to the secretCounter: public class MyClass implements PropertyChangeListener { private PropertyChangeSupport propertySupport = new PropertyChangeSupport(this); public MyClass() { propertySupport.addPropertyChangeListener(this); } public void propertyChange(PropertyChangeEvent evt) { System.out.println("property changing: " + evt.getPropertyName()); } public static void main(String[] args) { MysteryClass mysteryClass = new MysteryClass(); // do logic which involves increment and getting the value of MysteryClass } } Unfortunately, this did not work and I have no debug messages printed out. Does anyone see what is wrong with my implementation of the PropertyChangeSupport and Listener interfaces? I want to print a debug statement whenever incrementCounter is called or the value of secretCounter changes.

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  • What is a good "Error Checking" Pattern (Java)?

    - by Jack
    I'll explain what I mean by input error checking. Say you have a function doSomething(x). If the function completes successfully doSomething does something and returns nothing. However, if there are errors I'd like to be notified. That is what I mean by error checking. I'm looking for, in general, the best way to check for errors. I've thought of the following solutions, each with a potential problem. Flag error checking. If doSomething(x) completes successfully return null. Otherwise, it returns a boolean or an error string. Problem: Side effects. Throwing an exception. Throw an exception if doSomething(x) encounters an error. Problem: If you are performing error checking for parameters only, throwing an IllegalArgumentExceptionseems inappropriate. Validating input prior to function call. If the error checking is only meant for the parameters of the function, then you can call a validator function before calling the doSomething(x) function. Problem: What if a client of the class forgets to call the validator function before calling doSomething(x)? I often encounter this problem and any help or a point in the right direction would be much appreciated.

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  • Java giving incorrect year values

    - by whistler
    Something very, very strange is occurring in my program, and I'm wondering if anyone out there has seen this occur before. And, if so, how to fix it. Basically, I am parsing an csv file...no problem there. One column contains a date and I am taking it in as a String and changing to a Date object. Again, no problem there. The code is as follows: SimpleDateFormat dateFormat = new SimpleDateFormat("MM/dd/yy hh:mm"); Date initialDate = new Date(); try { initialDate = dateFormat.parse(rows.get(0)[8]); System.out.println(initialDate); } catch (ParseException e) { // TODO Auto-generated catch block e.printStackTrace(); } Of course, I'm parsing other columns as well (and those are working fine). So, when I run my program for a small csv file (2.8 MB), the dates come out (i.e. are parsed) perfectly. However, when I run the program for a large csv file (25 MB), the dates are a hot mess. For example, take a look at the year values I am getting (the following is just a tiny portion of the println output from the code above): 1000264 at Sun Nov 05 15:30:00 EST 2186 1000320 at Sat Mar 04 17:30:00 EST 2169 1000347 at Sat Apr 01 09:45:00 EDT 2169 1000413 at Tue Jul 09 13:00:00 EDT 2182 1000638 at Fri Dec 11 13:45:00 EST 2167 1000667 at Wed Dec 10 10:00:00 EST 2188 1000690 at Mon Jan 02 13:00:00 EST 2169 1000843 at Thu Feb 11 13:30:00 EST 2196 In actuality, the years are in the realm of 1990-2006 or so. Again, this does not happen with the small csv file. Does anyone know what's going on here and how I can fix it? I need to process the large csv file (the small one was just for testing purposes). By request, here are the actual dates in the csv file and after that the value given by the code above: 5/20/03 15:30 5/20/03 15:30 8/30/04 9:00 8/30/04 9:00 12/20/04 10:30 12/20/04 10:30 Sun Nov 05 15:30:00 EST 2186 Sun Nov 05 15:30:00 EST 2186 Sun Nov 05 15:30:00 EST 2186 Thu Dec 08 09:00:00 EST 2196 Tue Dec 12 10:30:00 EST 2186 Tue Dec 12 10:30:00 EST 2186

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  • Java: How to make this Serializable?

    - by Hasslarn
    I dont know that much about Serializable, but i need this class to be. How to achieve it? package helpers; public class XY implements Comparable<XY> { public int x; public int y; public XY (int x, int y) { this.x = x; this.y = y; } public int compareTo( XY other ) { String compare1 = this.x + "-" + this.y; String compare2 = other.x + "-" + other.y; return compare1.compareTo( compare2 ); } public String toString() { return this.x + "-" + this.y; } } As of now i cant send it as an object with outputstream..I´ve tried just to implement Serializable but it doesnt do the trick!

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  • Java - String Pool

    - by Gogi
    What is meant by String Pool ? What is difference between the following declarations : String s="hello"; String s=new String("hello"); Is there any difference between the Storing of this two strings by JVM ?

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  • deleting a file in java while uploading it in other thread

    - by user369507
    i'm trying to build a semi file sharing program, when each computer acts both as a server and as a client. I give multiple threads the option to DL the file from my system. also, i've got a user interface that can recieve a delete message. my problem is that i want that the minute a delete message receieved, i wait for all the threads that are DL the file to finish DL, and ONLY than excute file.delete(). what is the best way to do it? I thought about some database that holds and iterate and check if the thread is active, but it seems clumsy. is there a better way? thanks

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  • java overloaded method

    - by Sean Nguyen
    Hi, I have an abstract template method: class abstract MyTemplate { public void something(Object obj) { doSomething(obj) } protected void doSomething(Object obj); } class MyImpl extends MyTemplate { protected void doSomething(Object obj) { System.out.println("i am dealing with generic object"); } protected void doSomething(String str) { System.out.println("I am dealing with string"); } } public static void main(String[] args) { MyImpl impl = new MyImpl(); impl.something("abc"); // --> this return "i am dealing with generic object" } How can I print "I am dealing with string" w/o using instanceof in doSomething(Object obj)? Thanks,

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  • JAVA: multiple files download at the same time?

    - by user319096
    hi guys, Is there any methods for downloading multiple files at the same time? That is, after select multiple files, click the download button, and choose the destination directory, the files selected will be downloaded at the same time. i googled it and not find any solutions, can anybody know? im using struts1 and spring2.

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  • JAVA: How do I accept input during a certain period of time only

    - by sebrock
    Im trying to do a simple game where I continually need input from players. This needs to happen during a certain time period only. Everything that is sent after that will be discarded. After the time period a new game starts. So: Start game Wait for input from all players during 10 seconds 10 secs no more input Calculate the winner and do some stuff Goto 1. I was thinking using a timer and timertask to keep track of time and maybe use a boolean variable that changes from "open" to "closed" after 10 seconds? Please give me some advise on this.

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  • java - Depth First Search - Perform DFS on a tree

    - by DJDonaL3000
    Im trying to perform DFS on a Minimum Spanning Tree which contains 26 nodes. Nodes are named 'A' to 'Z' and the tree is undirected. I have an empty function called DFS here that I am trying to write, which (i presume) takes in the tree (a 2D array) a startNode (randomly selected node 'M') and the endNode (randomly selected node 'Z'). The weights of connected nodes are identified in the 2D array parameter, but how do I actually get started visiting nodes? All that is required is to print each nodeName in the order of the DFS traversal. Do I need to create a Node_class for each node in the 2d array??

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  • Regex to match a Java method signature

    - by nitesh
    I am having this particular requirement where a method has to be identified by different regular expressions for different components. For example, there need to be a regex for return parameter, one for method name, one for argument type and one for argument name. I was able to come up with an expression till this step as follows - ([^,]+) ([^,]+)\((([^,]+) ([^,]+))\) It works well for a method signature like - ReturnType foo(Arg parameter) The regular expression identifies ReturnType, foo, Arg and parameter separately. Now the problem is that a method can have no/one/multiple arguments separated by commas. I am not able to get a repeating expression for this. Help will be appreciated.

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