Java教程
java学习第21天
类与接口关系示例：
package jicheng.com;
public interface Inter1 {
}
package jicheng.com;
public interface Inter2 {
}
package jicheng.com;
public interface Inter3 extends Inter1,Inter2
{
}
package jicheng.com;
public class Interimpl extends
Object implements Inter3,Inter2,Inter1
{
}
抽象类与接口的区别：
成员区别：（抽象类）变量、常量，有构造方法，有抽象方法也有非抽象方法。
（接口）常量；抽象方法。
关系区别：类与类是继承且是单继承，类与接口是实现，可以是单实现，也可以多实现。接口与接口是继承可以单继承也可以多继承。
设计理念区别：（抽象类）对类抽象，包括属性和行为，（接口）对行为抽象，主要是行为。
举例：手机在发明之前只能打电话、发短信，发展后能够上网。
定义一个手机抽象类，有打电话发短信功能，定义一个上网的接口。
package jicheng.com;
public class Phone {
public Phone()
{
}
public void call(){
System.out.println("打电话");
}
public void message(){
System.out.println("发短信");
}
}
package jicheng.com;
public interface Surf
{
public abstract void surf();
}
package jicheng.com;
public class NewPhone extends
Phone implements Surf
{
@Override
public void surf()
{
System.out.println("surf
the internet");
}
public NewPhone()
{
}
public static void main(String[] args) {
NewPhone n= new NewPhone();
n.surf();
n.call();
n.message();
}
}
案例：我们现有乒乓球运动员和篮球运动员，乒乓球教练和篮球教练。为了出国交流，跟乒乓球相关的人员都需要学习英语。请用所学知识分析，这个案例需要哪些类哪些接口，并用代码实现。
分析：由具体到抽象。从具体篮球运动员类，乒乓球运动员类抽象出运动员类。从篮球教练类和乒乓球教练类抽象出教练类，从教练类和运动员类抽象出人类，定义一个学习英语接口，最后需要一个测试类。222
package anli;
public interface SpeakE {
public void speakEnglish();
}
package anli;
public abstract class People {
private int age;
private String
name;
public People()
{
}
public People(int age, String name) {
this.age = age;
this.name = name;
}
public int getAge()
{
return age;
}
public void setAge(int age) {
this.age = age;
}
public String
getName() {
return name;
}
public void setName(String
name) {
this.name = name;
}
public abstract void eat();
public abstract void work();
}
package anli;
public abstract class Coach extends People{
public Coach()
{
}
public Coach(int age, String name) {
super(age,
name);
}
public abstract void teach();
}
package anli;
public abstract class Player extends People
{
public Player()
{
}
public Player(int age, String name) {
super(age,
name);
}
public abstract void study();
}
package anli;
public class PingpangCoach extends Coach
implements SpeakE {
public PingpangCoach()
{
}
public PingpangCoach(int age, String name) {
super(age,
name);
}
@Override
public void eat()
{
System.out.println("吃白菜，喝小米粥");
}
@Override
public void work()
{
System.out.println("乒乓球教练一天工作3小时");
}
@Override
public void teach()
{
System.out.println("乒乓球教练教发球和接球");
}
@Override
public void speakEnglish()
{
System.out.println("乒乓球教练讲英语");
}
}
package anli;
public class BasketballCoach extends Coach
{
public BasketballCoach()
{
}
public BasketballCoach(int age, String name) {
super(age,
name);
}
@Override
public void eat()
{
System.out.println("吃牛肉，喝牛奶");
}
@Override
public void work()
{
System.out.println("篮球教练一天工作6小时");
}
@Override
public void teach()
{
System.out.println("篮球教练教运球和扣球");
}
}
package anli;
public class BasketballPlayer extends Player {
public BasketballPlayer() {
}
public BasketballPlayer(int age, String name) {
super(age, name);
}
@Override
public void eat() {
System.out.println("吃牛肉，喝牛奶");
}
@Override
public void work() {
System.out.println("篮球运动员一天训练8个小时");
}
@Override
public void study() {
System.out.println("篮球运动员学习扣篮和运球");
}
}package anli;
public class PingpangPlayer extends Player implements SpeakE {
public PingpangPlayer() {
}
public PingpangPlayer(int age, String name) {
super(age, name);
}
@Override
public void eat() {
System.out.println("乒乓球运动员吃蔬菜，喝米粥");
}
@Override
public void work() {
System.out.println("乒乓球运动员一天训练4小时");
}
@Override
public void study() {
System.out.println("乒乓球运动员学习发球和接球");
}
@Override
public void speakEnglish() {
System.out.println("乒乓球运动员讲英语");
}
}
package anli;
public class Demo {
public static void main(String[] args) {
System.out.println("教练员示例：");
PingpangCoach c1=new PingpangCoach(48,"刘国梁");
c1.eat();
c1.work();
c1.teach();
c1.speakEnglish();
System.out.println(c1.getName()+","+c1.getAge());
System.out.println("---------------");
System.out.println("运动员示例：");
BasketballPlayer b1=new BasketballPlayer(28,"姚明");
b1.eat();
b1.work();
b1.study();
System.out.println(b1.getName()+","+b1.getAge());
}
}
D:\Java\jdk-16.0.1\bin\java.exe -Didea.launcher.port=63736 "-Didea.launcher.bin.path=D:\IntelliJ IDEA 2018.2.8\bin" -Dfile.encoding=UTF-8 -classpath "C:\Users\dell\IdeaProjects\java学习\out\production\java学习;D:\IntelliJ IDEA 2018.2.8\lib\idea_rt.jar" com.intellij.rt.execution.application.AppMainV2 anli.Demo
教练员示例：
吃白菜，喝小米粥
乒乓球教练一天工作3小时
乒乓球教练教发球和接球
乒乓球教练讲英语
刘国梁,48
---------------
运动员示例：
吃牛肉，喝牛奶
篮球运动员一天训练8个小时
篮球运动员学习扣篮和运球
姚明,28
Process finished with exit code 0
类名作为形参和返回值
方法的形参是类名，其实需要的是该类的对象
方法的返回值是类名，其实返回的是该类的对象
示例：
package anli;
public class Cat {
public void eat(){
System.out.println("猫吃鱼");
}
}
package anli;
public class CatOperator {
public void useCat(Cat
c){
c.eat();
}
public Cat
getCat(){
Cat c=new Cat();
return c;
}
}
package anli;
public class CatDemo {
public static void main(String[] args) {
CatOperator c=new CatOperator();
Cat c1=new Cat();
c.useCat(c1);
Cat c2=c.getCat();
c2.eat();
}
}
D:\Java\jdk-16.0.1\bin\java.exe -Didea.launcher.port=64606 "-Didea.launcher.bin.path=D:\IntelliJ IDEA 2018.2.8\bin" -Dfile.encoding=UTF-8 -classpath "C:\Users\dell\IdeaProjects\java学习\out\production\java学习;D:\IntelliJ IDEA 2018.2.8\lib\idea_rt.jar" com.intellij.rt.execution.application.AppMainV2 anli.CatDemo
猫吃鱼
猫吃鱼
Process finished with exit code 0
抽象类名作为形参和返回值
方法形参是抽象类名，其实需要的是该抽象类的子类对象
方法的返回值是抽象类名，其实返回值是该抽象类的子类对象
示例
package anli;
public abstract class Animal {
public abstract void eat();
}
package anli;
public class Dog extends
Animal {
@Override
public void eat()
{
System.out.println("狗吃骨头");
}
}
package anli;
public class AnimalOperator {
public void useAnimal(Animal
a){
a.eat();
}
public Animal
getAnimal() {
Animal a = new Dog();
return a;
}
}
package anli;
public class AnimalDemo1 {
public
static void main(String[]
args) {
AnimalOperator a=new AnimalOperator();
Animal a1=new Dog();
a.useAnimal(a1);
Animal a2=a.getAnimal();
a2.eat();
}
}
D:\Java\jdk-16.0.1\bin\java.exe -Didea.launcher.port=57645 "-Didea.launcher.bin.path=D:\IntelliJ IDEA 2018.2.8\bin" -Dfile.encoding=UTF-8 -classpath "C:\Users\dell\IdeaProjects\java学习\out\production\java学习;D:\IntelliJ IDEA 2018.2.8\lib\idea_rt.jar" com.intellij.rt.execution.application.AppMainV2 anli.AnimalDemo1
狗吃骨头
狗吃骨头
Process finished with exit code 0
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