This example lets you treat your computer like a piece of paper and your mouse like a hole puncher. The user should be able to click anywhere on the window and create holes (GOvals).

Make a constant that describes the radius of the holes you will punch. 10 is a good size for this. Remember that GOvals want to see a double for this variable (not an int). Then add a mouse listener and create a draw method to react with every time the user punches a new hole.

## Solution

/**
* Class: HolePuncher
* -----------------
* A program that draws filled black circles on the screen whenever
* the mouse
* is pressed.
*/
public class HolePuncher extends GraphicsProgram {
/* The radius of each hole that we punch. */
private static final double HOLE_RADIUS = 10;

public void run() {
}

/**
* Draws a black circle centered at the mouse location whenever the mouse
* is pressed.
*/
public void mousePressed(MouseEvent e) {
double x = e.getX() - HOLE_RADIUS;
double y = e.getY() - HOLE_RADIUS;

GOval hole = new GOval(x, y, 2 * HOLE_RADIUS, 2 * HOLE_RADIUS);
hole.setFilled(true);