Java Graphics_4
package com.han;import java.awt.Canvas;import java.awt.Graphics;import javax.swing.JFrame;@SuppressWarnings("serial")public class Graphics_4 extends JFrame {public Graphics_4() {// TODO Auto-generated constructor stubCanvas canvas = new Canvas() {@Overridepublic void paint(Graphics g) {//super.paint(g); // for the one containing children components, this is necessary.int[] xPoints = { 10, 50, 10, 50 };int[] yPoints = { 10, 10, 50, 50 };//int nPoints = 3;int nPoints = 4;g.drawPolygon(xPoints, yPoints, nPoints);int[] xPoints2 = { 60, 100, 100, 60 };int[] yPoints2 = { 10, 10, 50, 50 };int nPoints2 = 4;g.drawPolygon(xPoints2, yPoints2, nPoints2);g.drawRect(110, 10, 40, 40);g.drawRoundRect(160, 10, 40, 40, 10, 10);}};this.add(canvas); // add()方法最早出现在Container中，所以我们无法在Canvas中添加组件。 }/** * @param args */public static void main(String[] args) {// TODO Auto-generated method stubGraphics_4 frame = new Graphics_4();frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);frame.setTitle("Draw polygon");frame.setSize(300, 200);frame.setVisible(true);}}