这个小程序如何编译不了

 class Person { String name ="No name"; public Person(String nm) { name = nm; } } class Employee extends Person { String empID = "0000"; [color=#FF0000]public Employee(String id) { empID = id; }//这里有什么错误阿？[/color]   } public class wren4255 {      public static void main(String[] args) { Employee e = new Employee("4321"); System.out.println(e.empID); } }

class Person { String name ="No name"; public Person(String nm) { name = nm; } } class Employee extends Person { String empID = "0000"; public Employee(String id) {      super(id);     empID = id;      } } public class wren4255 {      public static void main(String[] args) { Employee e = new Employee("4321"); System.out.println(e.empID); } }
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Java code
class Person { String name ="No name"; public Person(){}; public Person(String nm) { name = nm; } } class Employee extends Person { String empID = "0000"; public Employee(String id) {           empID = id;      } } public class wren4255 {      public static void main(String[] args) { Employee e = new Employee("4321"); System.out.println(e.empID); } }
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探讨

答：父类Person 中你要定义一个默认构造器。 
这是因为： 
public Employee(String id) { empID = id; } 
在编译时就是： 
public Employee(String id)  
{  
super();//这是编译程序自动加上的。而你Person中又没有定义无参的构造器。所以出错了。因此：你自己或者明确调用：super("..."); 
empID = id;  
} 

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Java code
class Person { String name ="No name"; public Person(String nm) { name = nm; } } class Employee extends Person { String empID = "0000"; [color=#FF0000]public Employee(String id) { empID = id; [/color]  }//这里有什么错误阿?[color=#FF0000]public Employee(String id) { super(id);empID = id; [/color] } public class wren4255 {      public static void main(String[] args) { Employee e = new Employee("4321"); System.out.println(e.empID); } }