Java之面向对象例子（二）

定义一个Book类，在定义一个JavaBook类继承他

//book类
package com.hanqi.maya.model;
public class Book {
    public String name;
    public int no;
    public  Book(){
        
    }
    public Book(String name1,int no1){
        name =name1;
        no=no1;
    }
    public String show(){
        return "书名是："+name+","+"页数："+no;
    }

}

//javaBook类继承
package com.hanqi.maya.model;
public class JavaBook extends Book{
    public String nandu;
    public JavaBook(){
        
    }
    public JavaBook(String nandu1){
        nandu=nandu1;
    }
    
    public String show(){
        String str=super.show();
        str+="难度是"+nandu;
        return str;
    }
}

//主函数
package com.hanqi.maya.main;
import com.hanqi.maya.model.JavaBook;
public class Main {
    public static void main(String[] args){
        JavaBook j=new JavaBook("21");
        j.name="21天";
        j.nandu="初级";
        j.no=20;
        String s=j.show();
        System.out.println(s); 
    }
}

super关键字。和this相对，对父类对象的引用

子类继承父类，子类的构造方法必须调用父类的构造方法，动用哪一个都行，如果子类没有去调用，子类会默认调用父类的空参构造方法，这个时候父类中如果没有空参构造方法，会报错

//父类
package com.hanqi.maya.model;
public class Book {
    public String name;
    public int no;
    public  Book(){
        
    }
    public Book(String name1,int no1){
        name =name1;
        no=no1;
    }
    public String show(){
        return "书名是："+name+","+"页数："+no;
    }
}

//子类
package com.hanqi.maya.model;
public class JavaBook extends Book{
    public String nandu;
    public JavaBook(){
        
    }
    public JavaBook(String name1,int nol,String nandu1){
        //父类对象的引用，这一行代表调用了父类构造函数
        //需要注意这里的括号里的参数，和方法里的内容，他们的类型的顺序要是一样的，和后面实例化传入的参数的顺序也要是一样的
        //子类继承父类，子类的构造方法必须调用父类的构造方法，动用哪一个都行，如果子类没有去调用，子类会默认调用父类的空参构造方法，这个时候父类中如果没有空参构造方法，会报错
        super(name1,nol);
        nandu=nandu1;
    }
    
    public String show(){
        String str=super.show();
        str+="难度是"+nandu;
        return str;
    }
}

//主方法
package com.hanqi.maya.main;
import com.hanqi.maya.model.JavaBook;
public class Main {
    public static void main(String[] args){
                //注意这里的类型顺序要和构造方法中一样
        JavaBook j=new JavaBook("21",20,"初级");
        /*j.name="21天";
        j.nandu="初级";
        j.no=20;
        */
        String s=j.show();
        System.out.println(s); 
    }
}

this关键字

this代表类本身

package com.hanqi.maya.model;

//book类
public class Book {
    public String name;
    public int no;
    public  Book(){
        
    }
    public Book(String name,int no){
        //这个类里的name
        this.name=name;
        this.no=no;
    }
    /*public Book(String name1,int no1){
        name =name1;
        no=no1;
    }*/
    public String show(){
        return "书名是："+name+","+"页数："+no;
    }
}

//JavaBook子类
package com.hanqi.maya.model;
public class JavaBook extends Book{
    public String nandu;
    public JavaBook(){
        
    }
    public JavaBook(String name1,int nol,String nandu1){
        //父类对象的引用，这一行代表调用了父类构造函数
        //需要注意这里的括号里的参数，和方法里的内容，他们的类型的顺序要是一样的，和后面实例化传入的参数的顺序也要是一样的
        //子类继承父类，子类的构造方法会默认调用父类的构造方法，，子类会默认加一个super()，
        super(name1,nol);
        nandu=nandu1;
    }
    
    public String show(){
        String str=super.show();
        str+="难度是"+nandu;
        return str;
    }
}

宠物栗子，可以显示，取名，玩耍，喂食，显示信息

//宠物类   父类
package com.hanqi.maya.model;

import java.util.Scanner;

public class Pet {
    public String lx;
    protected String name;//1
    protected int sex;//1
    protected int age;
    protected int happy;//80
    protected int healthy;//100
    protected int hungry;//80
    public static int uName;
    public Pet(){
    }
    public Pet(int sex){
        this.sex=sex;
        this.age=1;
        this.happy=80;
        this.healthy=100;
        this.hungry=80;
    }

    public void playGame(){
        if(!check()){
            System.out.println("各项属性值不能为负数");
            return;
        }
        System.out.println(this.name+"正在和你玩耍");
        this.happy+=10;
        this.healthy-=5;
        this.hungry+=12;
    }
    /*public void quName(){    
        Scanner sca=new Scanner(System.in);
        String s = sca.nextLine();
        this.name=s;
    }*/
    public void eat(){
        if(!check()){
            System.out.println("各项属性值不能为负数");
            return;
        }
        System.out.println(this.name+"正在吃饭");
        this.healthy+=5;
        this.hungry-=20;
    }
    public boolean check(){
        if(this.happy>=0&&this.healthy>=0&&this.hungry>=0){
            return true;
        }
        if(happy<0){
            happy=0;
        }
        if(healthy<0){
            healthy=0;
        }
        if(hungry<0){
            hungry=0;
        }
        return false;
    }
    
        public String getName() {
            return name;
        }
        public void setName(String name) {
            this.name = name;
        }
        public int getSex() {
            return sex;
        }
        public void setSex(int sex) {
            this.sex = sex;
        }
        public int getAge() {
            return age;
        }
        public void setAge(int age) {
            this.age = age;
        }
        public int getHappy() {
            return happy;
        }
        public void setHappy(int happy) {
            this.happy = happy;
        }
        public int getHealthy() {
            return healthy;
        }
        public void setHealthy(int healthy) {
            this.healthy = healthy;
        }
        public int getHungry() {
            return hungry;
        }
        public void setHungry(int hungry) {
            this.hungry = hungry;
        }
    
}

//猫类  子类
package com.hanqi.maya.model;

public class Cat extends Pet{
    public Cat(){
        
    }
    public Cat(int catSex){
        super(catSex);
    }
    public void show(){
        System.out.println("名称："+this.name);
        System.out.println("性别："+this.sex);
        System.out.println("年龄："+this.age);
        System.out.println("开心值："+this.happy);
        System.out.println("健康值："+this.healthy);
        System.out.println("的饥饿值："+this.hungry);
    }

}

//主方法
package com.hanqi.maya.model;
import java.util.Scanner;
public class Main {
    public static void main(String[] args) {
        Cat cat=new Cat(1);
        Scanner sc=new Scanner(System.in);
        boolean flag=true;
        while(flag){
            printControl();
            String s=sc.nextLine();
            if("0".equals(s)){
                String quna=sc.nextLine();
                cat.name=quna;
            }else if("1".equals(s)){
                cat.show();
            }else if("2".equals(s)){
                cat.eat();
            }else if("3".equals(s)){
                cat.playGame();
            }else if("bye".equals(s)){
                System.out.println("bye bye");
                flag=false;
            }
            
        }
        sc.close();
    }
    public static void printControl(){
        System.out.println("x.选择宠物");
        System.out.println("0.给宠物取个名字吧");
        System.out.println("1 .显示信息");
        System.out.println("2 .吃饭");
        System.out.println("3 .玩游戏");
    }
}