how to switch if and else statements to try and catch

so i made this program but I have to change the if and else statements to try and catch. any help will be greatly appreciated :) here is the code:

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

public class ShowIndex extends Applet implements ActionListener

{  int [] number =new int[100];
   Random r= new Random();
   Label indexlabel = new Label(" index:");
   TextField indexfield = new TextField(10);

   Label valuelabel = new Label("value:");
   TextField valuefield = new TextField(10);

   Button showButton = new Button ("Show Element");
   public void init()
      { int i;
        for(i=0;i<100;i++)
          number[i]=r.nextInt(1000)+1;  // random number between 1 and 1000 
        add(indexlabel);
        add(index开发者_如何学JAVAfield);
        add(valuelabel);
        add(valuefield);
        add(showButton);

        showButton.addActionListener(this);
        valuefield.setEditable(false);

      }
   public void actionPerformed(ActionEvent e)     
      { String inputString;
        int num;
        inputString=indexfield.getText();
        num=Integer.parseInt(inputString);
        if(num>99 ||num<0)
          valuefield.setText("Outof Bound");
        else      
          valuefield.setText(number[num]+"");

      }
}

Don't use exception handling as flow-control mechanism. Retain the if-clause.

Java has a great tutorial set.

I suggest going through the Exceptions section: (covering try/catch): http://download.oracle.com/javase/tutorial/essential/exceptions/

Try this:

try{
    valueField.setText(number[num]+"");
}catch(ArrayIndexOutOfBoundsException e){
    valueField.setText("Out of bound");
}

One way is to rewrite your actionPerformed function:

public void actionPerformed(ActionEvent e) { 

    String inputString;
    int num;
    inputString=indexfield.getText();
    num=Integer.parseInt(inputString);

    try {
       valuefield.setText(number[num]+"");
    }
    catch (Exception e) {
       valuefield.setText("Outof Bound");
    }

    // old version
    /*
    if(num>99 ||num<0)
      valuefield.setText("Outof Bound");
    else      
      valuefield.setText(number[num]+"");
    */

  }

I won't explain to you how this code works. It probably won't even compile, I haven't tried. Do a little research. Look at the ideas and try to see how they fit together. Research about array bounds, in array and List format. And the line

catch (Exception e) {

is a bit generic, I'm sure you can improve it.

Are you saying "I have to" because the teacher/boss told you to, or because you assume you have to? What's driving this change? A little thought about what the basic objective might reveal there's no need for a change after all.