继承 封装 多态 java的三大特性

import java.util.Scanner;

class A{
    int ivar = 7;
    void m1(){
        System.out.print("A's m1, ");
    }
    void m2(){
        System.out.print("A's m2, ");
    }
    void m3(){
        System.out.print("A's m3, ");
    }
}

class B extends A{
    void m1(){
        System.out.print("B's m1, ");
    }
}

class C extends B{
    void m3(){
        System.out.print("C's m3, "+(ivar + 6));
    }
}
public class Main{
    public static void main(String args[]){
        A a = new A();
        B b = new B();
        C c = new C();
        A a2 = new C();

        a.m1();
        b.m1();
        c.m3();
    }
}

运行结果：

A's m1, B's m1, C's m3, 13

//下面是一个很好的多态的例子

package com.company;

public class Main {
    public static void main(String[] args) {
        Animal dog = new Dog("旺财");
        Animal cat = new Cat("招财猫");
        dog.eat();
        cat.eat();
    }
}

class Animal
{
    private String name;
    public Animal(String name){
        this.name = name;
    }

    public void eat(){

    }
}

class Dog extends Animal
{
    public Dog(String name) {
        super(name);
    }
    public void eat(){
        System.out.println("吃骨头");
    }
}

class Cat extends Animal
{
    public Cat(String name){
        super(name);
    }
    public void eat(){
    System.out.println("吃鱼肉");
    }
}

运行结果：

吃骨头
吃鱼肉