题目

定义4个类，MyShape、MyLine、MyRectangle和MyOval，其中MyShape是其他三个类的父类。MyShape为抽象类，包括图形位置的四个坐标；一个无参的构造方法，将所有的坐标设置为0；一个带参的构造函数，将所有的坐标设置为相应值；每个坐标的设置和读取方法；abstract void draw(Graphics g)方法。MyLine类负责画直线，实现父类的draw方法；MyRectangle负责画矩形，实现父类的draw方法；MyOval负责画椭圆，实现父类的draw方法。编写一个应用程序，使用上面定义的类，随机选取位置和形状，绘制20个图形。
 

代码

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

public class shapeDrawing {
	//固定套路
	public static void main(String[] args)
	   {
	      DrawFrame frame=new DrawFrame();
	      frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
	      frame.setVisible(true);
	   }
}

//JFrame创建窗体
class DrawFrame extends JFrame
{
	public DrawFrame()
	{
		setTitle("Shapes");
	    setSize(400,400);
	    
	    //窗体中加入面板
	    DrawPanel panel = new DrawPanel();
	    add(panel);
	}
}

//JPanel在面板中显示信息
class DrawPanel extends JPanel
{
	//重写paintComponent方法
	public void paintComponent(Graphics g)
	{
		super.paintComponent(g);
		
		MyShape s;
		double c1,c2,c3,c4;
		for(int i=0;i<5;i++)
		{
			//生成四个随机数
			c1=Math.random()*200;
			c2=Math.random()*200;
			c3=Math.random()*200;
			c4=Math.random()*200;
			
			//图形绘制
			s=new MyLine(c1,c2,c3,c4);
			s.draw(g);
			s=new MyRectangle(c2,c1,c3,c4);
			s.draw(g);
			s=new MyOval(c4,c3,c2,c1);
			s.draw(g);
		}
	}
}

//抽象类MyShape,为其他三个类的父类
abstract class MyShape
{
	//四个坐标
	private double coordinate1;
	private double coordinate2;
	private double coordinate3;
	private double coordinate4;
	
	//无参构造
	public MyShape()
	{
		coordinate1=0;
		coordinate2=0;
		coordinate3=0;
		coordinate4=0;
	}
	
	//含参构造
	public MyShape(double a,double b,double c,double d)
	{
		coordinate1=a;
		coordinate2=b;
		coordinate3=c;
		coordinate4=d;
	}
	
	//抽象方法
	public abstract void draw(Graphics g);

	//设置和获取四个坐标
	public double getCoordinate1() {
		return coordinate1;
	}

	public void setCoordinate1(double coordinate1) {
		this.coordinate1 = coordinate1;
	}

	public double getCoordinate2() {
		return coordinate2;
	}

	public void setCoordinate2(double coordinate2) {
		this.coordinate2 = coordinate2;
	}

	public double getCoordinate3() {
		return coordinate3;
	}

	public void setCoordinate3(double coordinate3) {
		this.coordinate3 = coordinate3;
	}

	public double getCoordinate4() {
		return coordinate4;
	}

	public void setCoordinate4(double coordinate4) {
		this.coordinate4 = coordinate4;
	}
}

//画直线
class MyLine extends MyShape
{
	//构造
	public MyLine(double a,double b,double c,double d)
	{
		super(a,b,c,d);
	}
	
	//画
	public void draw(Graphics g)
	{
		Graphics2D g2=(Graphics2D)g;
		//四个坐标为:startx,starty,endx,endy
		Line2D line=new Line2D.Double(getCoordinate1(),getCoordinate2(),getCoordinate3(),getCoordinate4());
		g2.draw(line);
	}
}

//画矩形
class MyRectangle extends MyShape
{
	//构造
	public MyRectangle(double a,double b,double c,double d)
	{
		super(a,b,c,d);
	}
	
	//画
	public void draw(Graphics g)
	{
		Graphics2D g2=(Graphics2D)g;
		//四个坐标为:startx,starty,width,height
		Rectangle2D rect=new Rectangle2D.Double(getCoordinate1(),getCoordinate2(),getCoordinate3(),getCoordinate4());
		g2.draw(rect);
	}
}

//画椭圆
class MyOval extends MyShape
{
	//构造
	public MyOval(double a,double b,double c,double d)
	{
		super(a,b,c,d);
	}

	public void draw(Graphics g)
	{
		Graphics2D g2=(Graphics2D)g;
		//四个坐标为:startx,starty,width,height
		Ellipse2D e=new Ellipse2D.Double(getCoordinate1(),getCoordinate2(),getCoordinate3(),getCoordinate4());
		g2.draw(e);
	}
}

运行结果