Java 入门25 继承 this super

 

 

 Person类

package com.ITheima.d7_extends;

public class Person {
    private String name;
    private  int age;

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    public int getAge() {
        return age;
    }

    public void setAge(int age) {
        this.age = age;
    }
}

Student类继承Person类

package com.ITheima.d7_extends;

public class Student extends Person{
    public  void study(){
        System.out.println(getName()+"好好学习");
    }
}

Teacher类继承Person类

package com.ITheima.d7_extends;

public class Teacher extends Person {
    public void teach() {
        System.out.println(getName()+"开始教导学生");
    }
}

案例

 Person1类

package com.ITheima.d8_extends;

public class Person1 {
    private String name;
    private int age;

    public void watch(){
        System.out.println("查看课表");
    }

    //无参构造器
    public Person1() {
    }

    //有参构造器
    public Person1(String name, int age){
        this.name=name;
        this.age=age;
    }

    //set get

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    public int getAge() {
        return age;
    }

    public void setAge(int age) {
        this.age = age;
    }
}

Student1类

package com.ITheima.d8_extends;

public class Student1 extends Person1 {
    private String stayClass;
    public void write(){
        System.out.println("填写听课反馈");
    }

    public String getStayClass() {
        return stayClass;
    }

    public void setStayClass(String stayClass) {
        this.stayClass = stayClass;
    }
}

Teacher1类

package com.ITheima.d8_extends;

public class Teacher1 extends Person1 {
    private String place;

    public void sendMsg(){
        System.out.println("发布问题");
    }

    public String getPlace() {
        return place;
    }

    public void setPlace(String place) {
        this.place = place;
    }
}

TestDemo11类

package com.ITheima.d8_extends;

import com.ITheima.d7_extends.Teacher;

public class TestDemo11 {
    public static void main(String[] args) {
        Student1 s=new Student1();
        s.setName("TOM");//继承父类
        s.setAge(11);//继承父类
        s.setStayClass("梅花");
        s.write();

        Teacher1 t=new Teacher1();
        t.setName("Lili");//继承父类
        t.setAge(49);//继承父类
        t.setPlace("嘎嘎");
        t.sendMsg();
    }
}

 

 

 

 

 

 

 方法重写

 @Override重写注释

 Phone父类

package com.ITheima.d8_extends;

public class Phone {
    public void call(){
        System.out.println("开始打电话");
    }

    public void sendMessage(){
        System.out.println("发送短信开始");
    }
}

NewPhone 子类

package com.ITheima.d8_extends;

public class NewPhone extends Phone{
    /**
     * 方法重写
     * @Override  放在重写后的方法上,作为重写是否正确的校验注解
     * 加上该注解后 如果重写错误,编译阶段会出现错误提示
     * (建议重写方法都加@Override注解,代码安全 ,优雅!)
     * 方法重写注意事项和要求
     * 1 重写方法的名称,形参列表与被重写的方法是的名称和参数列表一致
     * 2 私有方法不能被重写
     * 3 这类重写父类方法时 访问权限必须大于或等于父类(暂时了解:缺省<protected<public)
     * 4 子类不能重写父类的静态方法,如果重写会报错
     */
    @Override
    public void call(){
        super.call();//调用父类的call方法
        System.out.println("支持饰视频通过~~~~");
    }

    /**
     * 方法重写
     */
    @Override
    public void sendMessage(){
        super.sendMessage();//调用父类的sendMessage方法
        System.out.println("支持图片发送");
    }
}

Test测试类

package com.ITheima.d8_extends;

public class Test {
    public static void main(String[] args) {
        NewPhone np=new NewPhone();
        np.call();
        np.sendMessage();
    }
}

 Animal类

package com.ITheima.d9_extends;

public class Animal {
    public Animal(){
        System.out.println("===父类Animal无参构造器被执行===");
    }
}

Cat类

package com.ITheima.d9_extends;

public class Cat extends Animal{
    public Cat(){
        super();//默认的 ,写不写 都有,默认就是执行父类无参数构造器
        System.out.println("===========子类Cat 无参构造执行=========");
    }

    public Cat(String name){
        System.out.println(name+"======子类有参构造器执行=======");
    }
}

Test类

package com.ITheima.d9_extends;

public class Test {
    public static void main(String[] args) {
        Cat c=new Cat();
        System.out.println("---------------------");
        Cat c1=new Cat("波斯猫");
    }
}

 Animal类

package com.ITheima.d9_extends;

public class Animal {
    private String name;
    private int age;

    //无参构造器
    public Animal() {
    }

    //有参构造器
    public Animal(String name,int age){
        this.name=name;
        this.age=age;
    }

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    public int getAge() {
        return age;
    }

    public void setAge(int age) {
        this.age = age;
    }
}

Cat类

package com.ITheima.d9_extends;

public class Cat extends Animal{
    //子类的私有成员变量
    private  String className;

    //无参构造器
    public Cat() {
    }

    //有参构造器
    public Cat(String name,int age,String className){
        //一定要访问父类的无参构造器(如果父类没有无参构造器 则需要手动访问父类的有参构造器 执行super(E element))
        super(name,age);//默认的 ,写不写 都有,默认就是执行父类无参数构造器
        this.className=className;
    }

    public String getClassName() {
        return className;
    }

    public void setClassName(String className) {
        this.className = className;
    }
}

Test类

package com.ITheima.d9_extends;

public class Test {
    public static void main(String[] args) {
        Cat c=new Cat("波斯猫",5,"幼儿园");
        System.out.println("---------------------");

        System.out.println(c.getAge());
        System.out.println(c.getName());
        System.out.println(c.getClassName());
    }
}

 this  super