重载构造函数

问题描述

从一本书中读取重载的构造函数后，我累了以下代码：

  public class Employee {
 
字符串名称; 
 int idNumber; 
 
 public Employee（）{
 this（JJ，0）; 
 System.out.println（name ++ idNumber）; 
} 
 
 public Employee（String name，int num）{
 
 this.name = name; 
 idNumber = num; 
 System.out.println（name +2nd+ idNumber）; 
} 
} 
 
 
 public class Object1 {
 
 public static void main（String [] args）{
 
 Employee emp = new Employee（）; 
} 
 
} 
  

OUTPUT：

  JJ第2 0 
 
 JJ 0 
  

我真的很困惑。为什么JJ第二0打印出来然后JJ 0??我创建了一个雇员对象emp，没有传递参数中的任何参数，不是先调用第一个构造函数。

解决方案

p> new Employee（）; 正在调用

  {
 this（JJ，0）; 
 System.out.println（name ++ idNumber）; 
} 
  

在此构造函数中

this（JJ，0）;

正在调用

public Employee（String name，int num）

构造函数， / p>

System.out.println（name +2nd+ idNumber）; 。

负责列印。

当此（JJ，0）; 将完成系统.out.println（name ++ idNumber）; 将被调用，你应该看到另一行

After reading overloaded constructors from a book, i tired the following code:

public class Employee {

    String name;
    int idNumber;

    public Employee(){
        this("JJ", 0);
        System.out.println(name +" "+ idNumber);
    }

    public Employee(String name, int num){

        this.name = name;
        idNumber = num;
        System.out.println(name +" 2nd "+ idNumber);
    }
}


public class Object1 {

    public static void main(String[] args) {

        Employee emp = new Employee();
    }

}

OUTPUT:

JJ 2nd 0

JJ 0

I am really confused. Why "JJ 2nd 0" printed out first then "JJ 0"?? I created an employee object emp and did not pass any args in the parameter, isn't suppose to call the first constructor first?

解决方案

new Employee(); is invoking

public Employee(){
    this("JJ", 0);
    System.out.println(name +" "+ idNumber);
}

In this constructor

this("JJ", 0);

is invoking

public Employee(String name, int num)

constructor, which ends with call

System.out.println(name +" 2nd "+ idNumber);.

which is responsible for printing

When this("JJ", 0); will finish System.out.println(name +" "+ idNumber); will be invoked and you should see another line

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