Rita ut 100 slumpmässiga rektanglar och ovaler.

import java.awt.*;
import javax.swing.*;
import java.lang.*;

public class RandomShape extends JFrame {
	private int n; //Instansvariabel
	public RandomShape() {}
	public RandomShape(int antal) {
		n = antal;
		for(int i=1; i<n; i++)
			add(generateRandomShape());
		setBackground(Color.white);
		setVisible(true);
		setSize(500,500);
		setDefaultCloseOperation(EXIT_ON_CLOSE);


	}

	public Component generateRandomShape() {
		double r1 = (int)(2*Math.random());
		if		(r1 == 0)
			return new RandomRect();
		else if (r1 == 1)
			return new RandomOval();
		else
			return null;
	}



	public static void main (String[] arg) {
		RandomShape r = new RandomShape(100);
	}
}

import java.awt.*;
import java.util.*;
import javax.swing.*;

public class RandomRect extends JPanel {
	private int width, height;
	public RandomRect() {
		width  = randomPixel();
		height = randomPixel();
		setPreferredSize(new Dimension(width, height));
		setOpaque(false);

	}

	@Override
	public void paintComponent(Graphics g) {
		super.paintComponent(g);
		g.setColor(Color.red);
		g.fillRect(randomPixel(),randomPixel(), width, height);
	}

	private int randomPixel() {
		int pix = (int)(Math.random()*400);
		return pix;
	}
}

import java.awt.*;
import java.util.*;
import javax.swing.*;

public class RandomOval extends JPanel {
	private int width, height;
	public RandomOval() {
		width  = randomPixel();
		height = randomPixel();
		setPreferredSize(new Dimension(width, height));
		setOpaque(false);

	}

	@Override
	public void paintComponent(Graphics g) {
		super.paintComponent(g);
		g.setColor(Color.green);
		g.fillOval(randomPixel(),randomPixel(), width, height);
	}

	private int randomPixel() {
		int pix = (int)(Math.random()*400);
		return pix;
	}
}