60 final关键词

 1 class Person{
 2     private String name;
 3     private int age;
 4     // final int age = 1;
 5 
 6     public Person(){
 7 
 8     }
 9 
10     public Person(String name , int age){
11         this.name = name;
12         this.age = age;
13 
14     }
15 
16     public void setName(String name){
17         this.name = name;
18     }
19 
20     public String getName(){
21         return name;
22     }
23 
24     public void setAge(int age){
25         this.age = age;
26     }
27 
28     public int getAge(){
29         return this.age;
30     }
31 
32     final public void fu(){
33 
34     }
35 
36 
37 }
38 
39 
40 class Student extends Person{
41     public Student(){};
42 
43     public Student(String name ,int age){
44         super(name,age);
45         // this.name = name;
46         // this.age = age;
47     }
48     public void study(){
49         System.out.print(getName());
50     }
51 
52     // public void fu(){
53     //     System.out.print("q");
54     // }
55 }
56 
57 class Teacher extends Person{
58     public Teacher(){};
59 
60     public Teacher(String name,int age){
61         super(name,age);
62     }
63 
64     public void teach(){
65         System.out.print("teach");
66     }
67 
68 
69 }
70 
71 class Demo2{
72     public static void main(String[] args) {
73         Student s = new Student();
74         s.setName("pan");
75         s.setAge(20);
76         s.study();
77 
78         final Student s1 = new Student("li",20);
79         s1.setAge(40);
80         s1  = new Student("ki",78);
81         System.out.println(s1.getAge());
82 
83     }
84 }

 1 class Teacher extends Person{
 2 
 3     final int age; // 无效.必须是赋值,默认值不行
 4 
 5     public Teacher(){};
 6 
 7     public Teacher(String name,int age){
 8         super(name,age);
 9     }
10 
11     public void teach(){
12         System.out.print("teach");
13     }
14 
15 
16 }