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 stub

reader = 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 stub

reader = 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 stub

reader = 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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作者：yang_tang

来源：CSDN

原文：https://blog.csdn.net/yang_tang/article/details/78070791?utm_source=copy

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