static

如代码示例：

代码中直接对调用类名进行赋值，该类的所有对象的university成员都为“传智大学”了，不用再一一赋值。

static的访问特点

多态 

多态中成员访问特点

多态的好处与弊端

多态中的转型

如示例代码：

 多态的代码案例示例：猫和狗

//Animal

package com;

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

    public Animal() {
    }

    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;
    }

    public void eat(){
        System.out.println("动物吃东西");
    }
}

//AnimalDemo

package com;

public class AnimalDemo {
    public static void main(String[] args) {
        Animal a=new Cat();
        a.setName("加菲");
        a.setAge(5);
        System.out.println(a.getName()+","+a.getAge());
        a.eat();

        a=new Cat("加菲",5);
        System.out.println(a.getName()+","+a.getAge());
        a.eat();

        Animal b=new Dog();
        b.setName("旺旺");
        b.setAge(6);
        System.out.println(b.getName()+","+b.getAge());
        b.eat();

        b=new Dog("旺旺",6);
        System.out.println(b.getName()+","+b.getAge());
        b.eat();
    }
}

//Cat
package com;

public class Cat extends Animal {
    public Cat(){
    }

    public Cat(String name,int age){
        super(name,age);
    }

    @Override
    public void eat() {
        System.out.println("猫吃鱼");
    }
}

//Dog
package com;

public class Dog extends Animal {
    public Dog() {
    }

    public Dog(String name, int age) {
        super(name, age);
    }

    @Override
    public void eat() {
        System.out.println("狗吃骨头");
    }
}