Java-继承，多态练习
1，实现如下类之间的继承关系，并编写Music类来测试这些类。
package com.chuoji.text01;
public class Instrument {
public void play()
{
System.out.println("弹奏音乐");
}
}
public class Brass extends Instrument {
public void play()
{
System.out.println("弹奏brass");
}
public void play2()
{
System.out.println("调用brass的play2");
}
}
public class Music {
public static void tune(Instrument i)
{
i.play();
}
public static void main(String[] args)
{
Wind w= new Wind();
Brass b= new Brass();
tune(w);
tune(b);
}
}
public class Music {
public static void tune(Instrument i)
{
i.play();
}
public static void main(String[] args)
{
Wind w= new Wind();
Brass b= new Brass();
tune(w);
tune(b);
}
}
2。
创建如下三个类：（People类中的三个方法分别输出一些信息，ChinaPeople 和AmericanPeople类重写父类的三个方法）。
package zhongqiuzuoye;
public class People {
protected double height;
protected double weight;
public double getHeight() {
return height;
}
public void setHeight(double height) {
this.height = height;
}
public double getWeight() {
return weight;
}
public void setWeight(double weight) {
this.weight = weight;
}
public void speakHello()
{
}
public void averageHeight()
{
}
public void averageWeight()
{
}
}
package zhongqiuzuoye;
public class ChinaPeople extends People{
public void chinaGoufu()
{
System.out.println("坐如钟，站如松");
}
public void speakHello()
{
System.out.println("你好");
}
public void averageHeight()
{
System.out.println("中国人平均身高为170cm");
}
public void averageWeight()
{
System.out.println("中国人平均体重是70kg");
}
}
package zhongqiuzuoye;
public class AmericnPeople extends People{
public void chinaGoufu()
{
System.out.println("直拳");
}
public void speakHello()
{
System.out.println("hello");
}
public void averageHeight()
{
System.out.println("美国人平均身高为180cm");
}
public void averageWeight()
{
System.out.println("美国人平均体重是80kg");
}
}
package zhongqiuzuoye;
public class TestPeople {
public static void main(String[] args) {
ChinaPeople c =new ChinaPeople();
c.speakHello();
c.averageHeight();
c.averageWeight();
AmericnPeople a=new AmericnPeople();
a.speakHello();
a.averageHeight();
a.averageWeight();
}
}
3.
编写一个Java应用程序，该程序包括3个类：Monkey类、People类和主类
E。要求：
(1) Monkey类中有个构造方法：Monkey (String s)，并且有个public void speak()
方法，在speak方法中输出“咿咿呀呀......”的信息。
(2)People类是Monkey类的子类，在People类中重写方法speak(),在speak方法
中输出“小样的，不错嘛！会说话了！”的信息。
(3)在People类中新增方法void think()，在think方法中输出“别说话！认真思考！”
的信息。
(4)在主类E的main方法中创建Monkey与People类的对象类测试这2个类的功
能。
父类：
package com.lianxi2;
public class Monkey {
private String s;
public String getS() {
return s;
}
public void setS(String s) {
this.s = s;
}
public Monkey(String s)
{
this.s=s;
}
public Monkey() {
super();
}
public void speak()
{
System.out.println("咿咿呀呀......");
}
}
子类：
package com.lianxi2;
public class People extends Monkey {
private String st;
public People(String s, String st) {
super(s);
this.st = st;
}
public void speak()
{
System.out.println("小样的，不错嘛！会说话了！");
}
public void think()
{
System.out.println("别说话！认真思考！");
}
}
测试：
package com.lianxi2;
public class M {
public static void main(String[] args) {
People pe=new People("你好","傻子");
pe.speak();
pe.think();
Monkey m=new Monkey();
m.speak();
}
}
结果：
4
定义类Human，具有若干属性和功能；定义其子类Man、Woman； 在主类Test中分别创建子类、父类和上转型对象，并测试其特性。
父类：
package com.lianxi3;
public class Human {
private String speak;
private String jump;
public String getSpeak() {
return speak;
}
public void setSpeak(String speak) {
this.speak = speak;
}
public String getJump() {
return jump;
}
public void setJump(String jump) {
this.jump = jump;
}
public Human(String speak, String jump) {
super();
this.speak = speak;
this.jump = jump;
}
public Human() {
super();
}
public void Jump()
{
System.out.println("跳："+jump);
}
public void Speak()
{
System.out.println("说："+speak);
}
public void as()
{
System.out.println("我能工作");
}
}
子类：
package com.lianxi3;
public class Man extends Human {
private String shui;
public String getShui() {
return shui;
}
public void setShui(String shui) {
this.shui = shui;
}
public void Shui()
{
System.out.println("睡"+shui);
}
}
测试：
package com.lianxi3;
public class Test {
public static void main(String[] args) {
Man m=new Man();
m.setJump("低");
m.setShui("长");
m.setSpeak("粗");
System.out.println("声音："+m.getSpeak()+" 跳："+m.getJump()+" 睡："+m.getShui());
//向上转型
Human h=new Man();
h.as(); //如果方法被重写，则调用子类的函数
//向下转型
Object ob=new Man();//先转形成等级最高的object
Man ma=(Man)ob; //在转型所需要的类型
}
}
5
28．按要求编写一个Java应用程序：
（1）定义一个类，描述一个矩形，包含有长、宽两种属性，和计算面积方法。
（2）编写一个类，继承自矩形类，同时该类描述长方体，具有长、宽、高属性，
和计算体积的方法。
（3）编写一个测试类，对以上两个类进行测试，创建一个长方体，定义其长、
宽、高，输出其底面积和体积。
父类：
package com.lianxi4;
public class Juxing {
private double chang;
private double kuan;
public double getChang() {
return chang;
}
public void setChang(double chang) {
this.chang = chang;
}
public Juxing(double chang, double kuan) {
super();
this.chang = chang;
this.kuan = kuan;
}
public Juxing() {
super();
}
public double mianJi()
{
return chang*kuan;
}
}
子类：
package com.lianxi4;
public class Tiji extends Juxing {
private double gao;
public Tiji(double chang, double kuan, double gao) {
super(chang, kuan);
this.gao = gao;
}
public double tiJi()
{
return super.mianJi()*gao;
}
}
测试：
package com.lianxi4;
public class Test {
public static void main(String[] args) {
Tiji ti=new Tiji(5,6,7);
System.out.println("面积："+ti.mianJi());
System.out.println("体积："+ti.tiJi());
}
}
结果：
6
编写一个Shape类，具有属性：周长和面积；
定义其子类三角形和矩形，分别具有求周长的方法。
定义主类E，在其main方法中创建三角形和矩形类的对象，
并赋给Shape类的对象a、b，使用对象a、b来测试其特性。
父类：
package com.lianxi5;
//抽象类
public abstract class Shape {
private double mianJi;
private double zhouchang;
public double getMianJi() {
return mianJi;
}
public void setMianJi(double mianJi) {
this.mianJi = mianJi;
}
public double getZhouchang() {
return zhouchang;
}
public void setZhouchang(double zhouchang) {
this.zhouchang = zhouchang;
}
public abstract double zhouchang();
}
子类;
package com.lianxi5;
public class Zc extends Shape {
private double x;
private double y;
private double z;
public double getX() {
return x;
}
public void setX(double x) {
this.x = x;
}
public double getY() {
return y;
}
public void setY(double y) {
this.y = y;
}
public double getZ() {
return z;
}
public void setZ(double z) {
this.z = z;
}
@Override
public double zhouchang() {
if((x+y)>z&&(x+z)>y&&(y+z)>x)
{
return x+y+z;
}
else
{
return 0;
}
}
}
package com.lianxi5;
public class Jxzc extends Shape {
private double x;
private double y;
public double getX() {
return x;
}
public void setX(double x) {
this.x = x;
}
public double getY() {
return y;
}
public void setY(double y) {
this.y = y;
}
@Override
public double zhouchang() {
return (x+y)*2;
}
}
测试;
package com.lianxi5;
public class Test {
public static void main(String[] args) {
Zc z=new Zc();
Jxzc j=new Jxzc();
z.setX(7);
z.setY(8);
z.setZ(9);
System.out.println(z.zhouchang());
}
}
结果：
