( ソース )

import java.awt.Graphics;
import java.awt.Color;
import java.awt.Event;
import java.awt.Point;

public class lines extends java.applet.Applet{

	final int MAXLINES = 60;
	Point starts[] = new Point[MAXLINES];
	Point ends[] = new Point[60];
	Point anchor;
	Point current_point;
	int current_line = 0;

	public boolean mouseDown(Event evt, int x, int y){
		anchor = new Point (x, y);
		return true;
	}

	public boolean mouseUp(Event evt, int x, int y){
		if(current_line < MAXLINES){
			addline(x, y);
		}else{
			System.out.println("Too many lines.");
		}
		current_point = null;
		repaint();
		return true;
	}
 	
	public boolean mouseDraw(Event evt, int x, int y){
		current_point = new Point(x, y);
		repaint();
		return true;
	}
	
	void addline(int x, int y){
		starts[current_line] = anchor;
		ends[current_line] = new Point(x, y);
		current_line++;
	}
	
	public void paint(Graphics g){
		int i;
		setBackground(Color.white);
		for ( i=0; i < current_line; i++ ){
		g.drawLine(starts[i].x, starts[i].y, ends[i].x, ends[i].y);
		g.setColor(new Color(i*i,i+4*i,i*i+3));
		}
		
		if(current_point != null)
	      g.drawLine(anchor.x, anchor.y, current_point.x, current_point.y);
		
	}
}