Random numbers and arrays

[Howard Ralston]

Howdy folks,
Let's try this again. This is a small program which is "supposed" to generate 3 random numbers from 1 to 6, not allowing any duplicates. Then it should put these numbers into an array of TextFields. It compiles but gives an exception in thread "main" NullPointerException. I figure that there is a problem with one of the arrays, but cannot figure out what the problem is. Any help would be greatly appreciated.
Thanks,
Howard

import java.awt.*;
import java.awt.event.*;
import java.util.Random;

public class HowNum extends Frame implements ActionListener{
 
  Button btn1;
  TextField [] t1;
  public HowNum(){
    setSize(200,200);
    setLayout(new GridLayout(2,3));
   
    t1 = new TextField[3];
    for(int i = 0;i<3;i++){
      add(t1[i]);  
    }
  
    btn1 = new Button("Press");
    add(btn1);
    btn1.addActionListener(this);
  }
  public static void main(String[]args){
    HowNum howard = new HowNum();
    howard.setVisible(true);
  }
   public void actionPerformed(ActionEvent e){
String[] str = new String[3];
int [] ints = new int[3];
       Integer[] numberList = new Integer[3];
Random rnd = new Random();
for(int i = 0;i < 3;i++){
   int newNumber = rnd.nextInt(6);
              for(int j = 0;j<numberList.length;j++){>
 if(numberList[j] != null){
     int temp = (numberList[j].intValue());
        if(temp == newNumber){ //number already exists
   newNumber = rnd.nextInt(6);
   j = -1;
}
 }
      }
   numberList[i] = new Integer(newNumber);
   ints [i] = numberList[i].intValue();
          str[i] = numberList [i].toString();
        }
for(int n = 0; n<3;n++){
 t1[n].setText(str[n]);
}  
    }
}

------------------

[Mike Curwen]

Here is the code...
It took me a while to remember that little thingy about arrays of objects being a little different.
I've also modified the random number generation to be a bit more compact.

import java.awt.*;
import java.awt.event.*;
import java.util.*;
public class HowNum extends Frame implements ActionListener{
  Button btn1;
  TextField t1, t2, t3;
  TextField[] fieldArray;
  public HowNum(){
    setLayout(new GridLayout(2,3));
    // this line only creates an array large enough to hold
    // 3 TextFields, it does not actually instantiate the TextFields
    fieldArray = new TextField[3];
    for(int i=0;i<3;i++){
        fieldArray[i] = new TextField();
        add(fieldArray[i]);
    }
    btn1 = new Button("Press");
    add(btn1);
    btn1.addActionListener(this);
    setSize(200,200);
    pack();
    show();
  } // HowNum()
  public static void main(String[] args){
    HowNum app = new HowNum();
    app.addWindowListener( new WindowAdapter() {
        public void windowClosing(WindowEvent e) {
            System.exit(0);
        }
    });
  } // main()
  public void actionPerformed(ActionEvent e){
    Random rnd = new Random();
    Vector v = new Vector();
    boolean done = false;
    while (!done) {
        Integer temp = new Integer(rnd.nextInt(6)+1);
        if (!v.contains(temp)) {
            v.add(temp);
        }
        done=(v.size()==3);
    }
    for(int n = 0; n<3;n++){
      fieldArray[n].setText(v.elementAt(n).toString());
    }
  } // actionPerformed()
} //end class

[Howard Ralston]

Thanks a lot, Mike. I won't have time to utilize your changes until tomorrow, but suddenly my headache is fading away.
I'm not familiar with the Vector class so this method did not even occur to me. I guess I need to look up the API for it in order to learn more about the provided methods.
Thanks again.
Howard