Java 1028 多态

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package com.lovo;/** * 图形类（父类） * @author 周博 */import java.awt.Color;import java.awt.Graphics;//如果一个类有抽象方法，这个类必须被声明为抽象类//抽象类不能实例化（不能创建对象），抽象类是专门用来被继承的；public abstract class Shape {protected int x, y;protected Color color;/** * 无参构造器 */public Shape(){}/** * 计算周长 * @return 图形的周长 */public abstract double getCircumfefence();  //抽象方法,没有实现   关键字：abstract/** * 计算面积 * @return图形的面积 */public abstract double getArea();/** * 绘画 * @param g 画笔 */public abstract void draw(Graphics g);public int getX() {return x;}public void setX(int x) {this.x = x;}public int getY() {return y;}public void setY(int y) {this.y = y;}public Color getColor() {return color;}public void setColor(Color color) {this.color = color;}}

package com.lovo;import java.awt.Graphics;public class Rectangle extends Shape {private int width, height;    /**     * 构造器     * @param w     * @param h     */public Rectangle(int width, int height) {this.width = width;this.height = height;}@Overridepublic double getCircumfefence() {   return 2 * (width + height);}@Overridepublic double getArea() {return width* height;}@Overridepublic void draw(Graphics g) {g.setColor(color);g.drawOval(x, y, width, height);}}

package com.lovo;import java.awt.Graphics;public class Circle extends Shape {private int radius;public Circle(int radius){this.radius = radius;}@Overridepublic double getCircumfefence() {    return 2 * Math.PI * radius;}@Overridepublic double getArea() {return  Math.PI * radius * radius;}@Overridepublic void draw(Graphics g) {g.setColor(color);g.drawOval(x - radius, y - radius, 2 * radius, 2 * radius);}}

package com.lovo;import java.awt.Color;import java.awt.Graphics;import javax.swing.JFrame;public class Polymorphism extends JFrame {private Shape[] shapes = new Shape[5];public Polymorphism(){this.setSize(800, 800);this.setResizable(false);this.setLocationRelativeTo(null);this.setDefaultCloseOperation(EXIT_ON_CLOSE);for(int i = 0; i < shapes.length; i ++){int num = (int) (Math.random() * 2);Shape currentShape  = null;switch(num){case 0:int ridius = (int) (Math.random() * 50 + 50);currentShape = new Circle(ridius);break;case 1:int width = (int) (Math.random() * 300 + 100);int height = (int) (Math.random() * 300 + 100);currentShape = new Rectangle(width,height);break;}int red = (int) (Math.random() * 256);int greed = (int) (Math.random() * 256);int blue = (int) (Math.random() * 256);currentShape.setColor(new Color(red, greed, blue));int x = (int) (Math.random() * 300 + 100);int y = (int) (Math.random() * 300 + 100);currentShape.setX(x);currentShape.setY(y);shapes[i] = currentShape;}}public void paint(Graphics g){super.paint(g);// for-e 循环打印for(Shape sh :shapes ){sh.draw(g);}}public static void main(String[] args) {new Polymorphism().setVisible(true);}}

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