class 类名1 extends 类名2{
    
    }

1、父类有有参构造器,子类无有参构造器,会报错?
答：子类实例化有参的对象时,默认调用父类的无参构造器,父类中存在无参构造器,不会报错,假如父类中没有无参构造器,
只有有参构造器,那么需要在子类构造器中添加super关键字,super关键字括号里面填相应的参数,调用父类有参构造器

2、为什么要调用父类的构造器?这样子做的意义何在?
答：调用父类的构造器是可以初始化父类继承下去的属性的.
注意：子类中如果有无参构造器,父类中一定也要有

 1 /*
 2 需求：有工人,农民,教师,科学家,服务生,其中,工人,农民,服务生只有基本工资.
 3      教师除基本工资外,还有课酬(元/天),科学家除基本工资外,还有年终奖,
 4      请你写出相关类,将各种类型的员工的全年工资打印出来;
 5 */
 6 class People{
 7     private double BaseSal; //基本工资
 8      double Bonus; //奖金
 9     public People(){
10 
11     }
12     public People(double BaseSal){
13         this.BaseSal=BaseSal;
14     }
15     public double getBaseSal(){ //基本薪资
16         return BaseSal*12;
17     }
18     public double getBonus(double sal){ //额外薪资
19         return Bonus;
20     }
21     public double getYearSal(double sal){ //年薪
22         return getBonus(sal)+getBaseSal();
23     }
24 }
25 
26 class Worker extends People{ //工人
27     public Worker(double BaseSal){
28         super(BaseSal);
29     }
30     public double getBonus(double sal){//额外薪资
31         return Bonus;
32     }
33 }
34 
35 class Waiter extends People { //服务员
36     public Waiter(double BaseSal){
37         super(BaseSal);
38     }
39     public double getBonus(double sal){ //额外薪资
40         return Bonus;
41     }
42 }
43 
44 class Scientist extends People { //科学家
45     public Scientist(double BaseSal){
46         super(BaseSal);
47     }
48     public double getBonus(double sal){ //额外薪资
49         return getBaseSal()*(8/10);
50     }
51         
52 }
53 
54 class Teacher extends People { //教师
55     public Teacher(double BaseSal){
56         super(BaseSal);
57     }    
58     public double getBonus(double sal){
59         return 12*30*sal;
60     }
61 }
62 class Farmer extends People { //农民
63     public Farmer(double BaseSal){
64         super(BaseSal);
65    }
66     public double getBonus(double sal){ //额外薪资
67         return sal;
68    }
69 }
70 
71 class  Demo1{
72     public static void main(String[] args) {
73         Farmer f=new Farmer(1200);//
74         Teacher t=new Teacher(2000);
75         System.out.println("农民年薪"+f.getYearSal(0));//
76         System.out.println("老师的薪资"+t.getYearSal(500));
77         Waiter w=new Waiter(4000);
78         System.out.println("服务员薪资:"+w.getYearSal(100000));
79 
80     }
81 }