java 类的继承

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这个星期主要是学习了Java中类的继承问题.继承就是由已有的类创建新类,通过子类继承父类的方法,实现一些功能.

下面就是老师布置作业的其中一个:

定义父类圆，通过继承，获得子类球、圆锥、圆柱，子类具有计算体积的功能。
1）新建文件夹Test1；
2）定义父类Circle，Circle具有保护成员变量半径r，并提供成员方法setR、getArea和带参数的构造函数；
3）子类球Ball具有获得体积的成员方法getValume；
4）子类圆锥Cone、圆柱Cylinder具有私有的成员变量高high、设置高的成员方法setHigh()和获得体积的getValume；
5）3个子类都提供带参数的构造函数；
6）3个子类在重设半径后，应获得正确的体积；
7）编写测试类进行测试

代码:

Circle.java

package test3;public class Circle {public static void main(String[] args) {// TODO Auto-generated method stub}protected double r;public void setR(double r) {this.r = r;}public double getArea() {return 3.14*r*r;}//public Circle(double r) {//super();//this.r = r;//}public Circle() {super();// TODO Auto-generated constructor stub}}

Ball.java

package test3;import java.util.Scanner;public class Ball extends Circle{public static void main(String[] args) {// TODO Auto-generated method stubreader = new Scanner(System.in);Ball ball =new Ball();double r;System.out.println("请输入圆的半径：");r = reader.nextDouble();ball.setR(r);System.out.println("体积：" + ball.getValumn());}private static Scanner reader;public double getValumn() {return getArea()*r*4/3;}public Ball() {super();// TODO Auto-generated constructor stub}}

Cone.java

package test3;import java.util.Scanner;public class Cone extends Circle{//public Cone(double r) {//super(r);//// TODO Auto-generated constructor stub//}//private double valumn;private double high;private static Scanner reader;public void setHigh(double high) {this.high = high;}public double getValumn() {return getArea() *high/3;}public Cone() {super();// TODO Auto-generated constructor stub}public static void main(String[] args) {// TODO Auto-generated method stubreader = new Scanner(System.in);Cone cone = new Cone();double high,r;System.out.println("请输入圆锥的高：");high = reader.nextDouble();System.out.println("请输入圆锥的半径：");r = reader.nextDouble();cone.setHigh(high);cone.setR(r);System.out.println("体积：" + cone.getValumn());}}

Cylinder.java

package test3;import java.util.Scanner;public class Cylinder extends Circle{public static void main(String[] args) {// TODO Auto-generated method stubreader = new Scanner(System.in);Cylinder cy = new Cylinder();double r,high;System.out.println("请输入的高：");high = reader.nextDouble();System.out.println("请输入半径：");r = reader.nextDouble();cy.setHigh(high);cy.setR(r);System.out.println("体积：" + cy.getValumn());}private double high;private static Scanner reader;public void setHigh(double high) {this.high = high;}public double getValumn() {return getArea() *high;}public Cylinder() {super();// TODO Auto-generated constructor stub}}

Java中类的继承,更多的可以查看http://www.cnblogs.com/dolphin0520/p/3803432.html,这里有详细的介绍,我大致就是看这个学习的.

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