60 final关键词

final 关键词

修辞类  类不能被继承

修辞成员变量 变量不能被改变

修改方法 方法无法覆写

 

变量如果是基本类型 是值 不能被改变

引用类型,地址不变,但是属性值可以改变

 

class Person{
    private String name;
    private int age;
    // final int age = 1;

    public Person(){

    }

    public Person(String name , int age){
        this.name = name;
        this.age = age;

    }

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

    public String getName(){
        return name;
    }

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

    public int getAge(){
        return this.age;
    }

    final public void fu(){

    }


}


class Student extends Person{
    public Student(){};

    public Student(String name ,int age){
        super(name,age);
        // this.name = name;
        // this.age = age;
    }
    public void study(){
        System.out.print(getName());
    }

    // public void fu(){
    //     System.out.print("q");
    // }
}

class Teacher extends Person{
    public Teacher(){};

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

    public void teach(){
        System.out.print("teach");
    }


}

class Demo2{
    public static void main(String[] args) {
        Student s = new Student();
        s.setName("pan");
        s.setAge(20);
        s.study();

        final Student s1 = new Student("li",20);
        s1.setAge(40);
        s1  = new Student("ki",78);
        System.out.println(s1.getAge());

    }
}

 

 

class Teacher extends Person{

    final int age; // 无效.必须是赋值,默认值不行

    public Teacher(){};

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

    public void teach(){
        System.out.print("teach");
    }


}