如何引用在不同类的 main 方法中声明的对象的属性

Question

I have 2 classes in 2 separate files. My first class in Person.java is shown below:

public class Person(){
    String name;
    public static void main(String[] args) {
        Person paul = new Person();
        paul.name = paul();
    }
}

How would I reference that ^ specific person object's name property (paul) in my second class: Family.java's main method? Inside of Family.java I've tried creating a new person object but i can't then reference the Person object, Paul,'s name property.

Pretty much in Family.java

public class Family(){
    public static void main(String[] args) {

    }
}

inside of the main method i want to get the paul object, which i created in Person.java's main method,'s name property

Answer 1

This cannot be done. Upon Person.main returning, paul falls out of scope and is no longer accessible, and becomes eligible for garbage collection.

You could instead do something like this:

public class Person{
    String name;
    static Person paul;
    public static void main(String[] args) {
        paul.name = "Paul"; //I assume you meant this?
    }
}

public class Family{
    public static void main(String[] args) {
        Person paul = Person.paul;
    }
}

But judging from what you're trying to do (and that you ahve two main methods) you may have a deeper issue.

Answer 2

You can have static member in your Person class then access in the Family class. You can define the getter for the name attribute for getting the name of the Person . Also you can keep both the class in one file, keeping only one of the class public, because file name should same as the public class. Also () are not required for declaring a class. As name is String type in the class, you can define an string literal for assigning to it.

public class Family {
  public static void main(String[] args) {
    Person person = Person.paul;
    String name = person.getName();
  }
}

class Person{
  private String name;
  static Person paul;

  public static void main(String[] args) {
    paul = new Person();
    paul.name = "paul";
  }

  public String getName() {
    return name;
  }

  public void setName(String name) {
    this.name = name;
  }    
}

PS : What are you trying to achieve with this code? Because two main method are not required. You can define an constructor in the Person class with an String argument. Create the Person object in you Family class as you need.