package com.org.sxt.overload;
public class OverLoad {

    public static void main(String[] args) {
        Person p = new Person();
        Person p1 = new Person(2);
        Person p2 = new Person(3, 22);
        System.out.println("p: " + p);
        System.out.println("p1: " + p1);
        System.out.println("p2: " + p2);
    }
}

class Person {
    int id;
    int age;

    Person() {
        id = 1;
        age = 20;
    }

    Person(int _id) {
        id = _id;
        age = 21;
    }

    Person(int _id, int _age) {
        id = _id;
        age = _age;
    }
    
    public String toString() {
        return "Person id=" + id + " age=" + age;
    }
}

------解决方案--------------------
在Person中重写toString()方法

public String toString(){
 return "this.id = " + this.id + "  this.age=" + this.age;
}

然后在main(）方法中
System.out.println(p.toString);
System.out.println(p1.toString);
System.out.println(p2.toString);

------解决方案--------------------
原理就是在下面语句中
System.out.println("p: " + p);

计算"p: " + p时会自动调用p.toString()
等价于
"p: " + p.toString()

如果这样写System.out.println(p);
也等价于
System.out.println(p.toString());