Exercise : jGRASP Debugger

Breakpoints help you debug programs (). Copy/paste this code into jGRASP:

public class Numbers {
    public static void main(String[] args) {
        int number = 42;
        for (int i = 1; i <= 1000; i++) {
            number = number * 37 % 103;
        }
        int number2 = number * number;
        System.out.println("result = " + number2);
    }
}

Set a breakpoint on the statement inside the for loop (line 5). Do this by moving your cursor to the beginning of that line until you see a stop-sign icon and then clicking.

continued on the next slide...

Exercise - jGRASP Debugger

Now you can debug the program by clicking on the debug icon (looks like a ladybug).
It will stop every time it hits line 5. Then you can see the values of variables i and number.
To continue running, press the top-left play or step buttons.
Using this approach, fill in the table below indicating what value number has when i has the given value. Keep in mind that you are figuring out what value number has just before it executes this line of code.
i = 1, number =
42
i = 2, number =
9
i = 3, number =
24
i = 4, number =
64

continued on the next slide...

Exercise - jGRASP Debugger

Click on the stop-sign a second time to get rid of it and then set a new stop point on line number 7. This will allow you to find out the value of number after the loop is done executing.
Again press "play" to start the programming running again.
At line 7, what is the value of number? 69

`i = 1, number =`		42
`i = 2, number =`		9
`i = 3, number =`		24
`i = 4, number =`		64