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Thread: problem in 2D array of TextField

  1. #1
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    Exclamation problem in 2D array of TextField

    I have a problem in this code.I can't display the array of Text Field.

    import javax.swing.*;
    import java.awt.*;
     
    public class Projct extends JFrame {
        int x=3;
     
    public Projct(){
     
        Container c=getContentPane();
        c.setLayout(new BorderLayout());
     
        JPanel p=new JPanel();
        //new GridLayout(x,x)
        c.add(p,BorderLayout.CENTER);
    JTextField [][] array=new JTextField[x][x];
        for(int i=0;i<x;i++){
             for(int j=0;j<x;j++){
     
               array[i][j].setText(" ");
     
                 p.add(array[i][j]);
     
     
     
    }
        }
     
    int m=x;
     double [][] data=new double [m][m];
     
         for(int i=0;i<m;i++){
             for(int j=0;j<m;j++){
                 if (i == j) {
                 data[i][j]=1;
              array[i][j].setText("1");
             array[i][j].setEnabled(false);
     
                 }
        else{
     
     
                data[i][j]=Double.parseDouble(array[i][j].getText());
                  data[j][i]=(1/data[i][j]);
                 }}}
     
     
     
        }
     
    public static void main(String[]arg){
        Projct f=new Projct();
        f.setTitle("AHP");
        f.setVisible(true);
        f.setSize(500, 500);
        f.setLocation(40,60);
       f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
     
    }
     
    }


  2. #2
    Administrator copeg's Avatar
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    Default Re: problem in 2D array of TextField

    Define can't display...does it compile? Are there any exceptions? (hint: see Common Java Mistakes)

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    Default Re: problem in 2D array of TextField

    Quote Originally Posted by copeg View Post
    Define can't display...does it compile? Are there any exceptions? (hint: see Common Java Mistakes)

    no it doesn't compile

    Exception in thread "main" java.lang.NullPointerException
    at Projct.<init>(Projct.java:20)
    at Projct.main(Projct.java:52)
    Java Result: 1
    BUILD SUCCESSFUL (total time: 1 second)




    i don't know the order of writing the arrays
    1st array is array of Text Field
    2nd array is array of values that will enter by user

    I want the result to be like this pic

  4. #4
    Administrator copeg's Avatar
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    Default Re: problem in 2D array of TextField

    no it doesn't compile

    Exception in thread "main" java.lang.NullPointerException
    Based upon that it sure looks like it compiles...a NullPointerException is a runtime exception . Did you have a look at the link I posted above? You've created an array without initializing its elements.
    Last edited by copeg; January 6th, 2011 at 08:18 PM.

  5. The Following User Says Thank You to copeg For This Useful Post:

    Eng.muslima (January 6th, 2011)

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    Default Re: problem in 2D array of TextField

    Quote Originally Posted by copeg View Post
    Based upon that it sure looks like it compiles...a NullPointerException is a runtime exception . Did you have a look at the link I posted above? You've created an array without initializing its elements.
    thanks for this information.

    I read
    Problem description: Forgetting to initialize a variable
    Problem description: Array Indices/Off by 1 errors

    but my problem is how can I initialize the variable of 2D array
    I want blank text fields then the user only type the values of upper triangle then the program will assign this values to the inverted triangle , diagonal will be always = 1 by setTextField

    I have an exam & I want to find the solve

  7. #6
    Administrator copeg's Avatar
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    Default Re: problem in 2D array of TextField

    but my problem is how can I initialize the variable of 2D array
    Do you mean something like this?
    String[] strings = new String[1];
    int len = strings[0].length();//NullPointerException, the value strings[0] was never initialized
    string[0] = new String("Testing");
    len = strings[0].length();//Now it has been initialized
    The same principle holds true for all objects. Nowhere in the code you posted above is there a "new JTextField()", so all the members of the array will be null until they are instantiated.
    Last edited by copeg; January 6th, 2011 at 09:07 PM.

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    Default Re: problem in 2D array of TextField

    Thank you very much
    array[ ][ ] is work and the frame is appear , now I have to complete my code then data [ ] [ ] will work

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