import?java.awt.*;
import?java.awt.event.*;
import?java.awt.geom.*;
import?java.util.*;
import?javax.swing.*;
public?class?SketchTest?{
	public?static?void?main（String[]?args）{
		Sketchframe?f?=?new?Sketchframe（）;
		f.setDefaultCloseOperation（Jframe.EXIT_ON_CLOSE）;
		f.setVisible（true）;
	}
}
class?Sketchframe?extends?Jframe{
	public?Sketchframe（）{
		this.settitle（“Sketch?frame“）;
		this.setSize（DEFAULT_WIDTHDEFAULT_HEIGHT）;
		this.add（new?SketchPanel（））;
	}

	public?static?final?int?DEFAULT_WIDTH?=?400;
	public?static?final?int?DEFAULT_HEIGHT?=?300;

}
class?SketchPanel?extends?JPanel{
	public?static?final?int?SMALL_INCRE?=?1;
	public?static?final?int?LARGE_INCRE?=?5;
	private?ArrayList?pl;
	private?Point2D?last;
	public?SketchPanel（）{
		pl?=?new?ArrayList（）;
		last?=?new?Point2D.Double（100100）;
		KeyHandler?h?=?new?KeyHandler（）;
????????????????MouseHandler?mo=new?MouseHandler（）;
		this.addKeyListener（h）;
????????????????this.addMouseListener（mo）;
		this.setFocusable（true）;
	}
public?void?paintComponent（Graphics?g）{
	Graphics2D?g2?=?（Graphics2D）g;
	super.paintComponent（g2）;
	
	for（Line2D?l:pl）{
	g2.