caught in an infinite loop in my try and catch coding.

[Mark Daniel]

I can't figure out why, but I think that I am caught in an infinite loop, the program compiles, and runs, however when I enter a number that is out of the range, it doesn't throw an error message. here is the code that I think contains the improper coding, if you need the full code I have attached it on notepad.
Thanks

 public void actionPerformed(ActionEvent e)
    {
        //read user input into variables
        int start = Integer.parseInt(startField.getText());
        int stop = Integer.parseInt(stopField.getText());
        int step = Integer.parseInt(stepField.getText());
        for (int i=0; i<16; i++)
        {
             boardDisplay[i].setBackground(Color.magenta);
             if(e.getActionCommand().equals("Clear"))
               boardDisplay[i].setBackground(Color.white);
             }
        for (int i=start; i<=stop; i+=step)
             {
             boardDisplay[i].setBackground(Color.yellow);
             if(e.getActionCommand().equals("Clear"))
               boardDisplay[i].setBackground(Color.white);
        }
        boolean condition=true;
        while (condition)
 
           {
            try
            {
                if (start < 0 | start > 16) throw new NumberFormatException();
                else condition = false;
 
            }
            catch (NumberFormatException g)
            {
            System.out.println("Only enter 0 to 15 in number format.");
            }
 
 
               }
        }
 
    public static void main(String[] args)
 
        {
            Checkerboard f = new Checkerboard();
            f.setBounds(50,100,300,400);
            f.setTitle("Checkerboard Array");
            f.setVisible(true);
    } //end of main
}
 

[Dheeraj Joshi]

There are couple of problems in the code.
You have declared an array of length 16

TextArea boardDisplay[] = new TextArea[16];
 

But in actionPerformed method. You try to fill these arrays.

for (int i=start; i<=stop; i+=step)
{
         boardDisplay[i].setBackground(Color.yellow);
         if(e.getActionCommand().equals("Clear"))
         boardDisplay[i].setBackground(Color.white);
}
 

Suppose start is 5 and stop is 55 and step is 5
your code tries to fill following items in array are changed with colour

boardDisplay[5]
boardDisplay[10]
boardDisplay[15]

These are legitimate entries. But now your for loop is not completed, since

i<=stop true (15 <= 55)

So for loop tries to run again increments i to 20 and tries to fill

boardDisplayp[20]

. This is out of bound (Remember your array is from 0-15 there is no 20th element and it throws array index out of bound exception.)

Solution is check the start stop values before executing these loops. And if they are out of range throw an error message in GUI and exit.

You can rewite like

int start = Integer.parseInt(startField.getText());
int stop = Integer.parseInt(stopField.getText());
int step = Integer.parseInt(stepField.getText());
 
try{
if ((start < 0 || start >= 16) || (stop<start) || (stop >= 16 || stop < 0)) throw new NumberFormatException();
else condition = false;
}
catch(Exception ex){
        System.out.println("Exception");
}
 

Regards
Dheeraj Joshi