Unable to see ArrayList elements in another object in Java

I'm trying to view the elements of an ArrayList in a different class but it shows that there is nothing. In the other class, you can see the element in the ArrayList though.

Here are the codes.

First class

import java.util.ArrayList;
public class Test {

ArrayList<String> inventory = new ArrayList<String>();

public void test() {
  inventory.add("item");
}

public void check() {
  System.out.println(inventory);
}

}

Second class

import java.util.ArrayList;
public class Test2 {

Test testObj = new Test();

public void test2() {
  System.out.println(testObj.inventory);
}

}

Main class

public class Main {

  public static void main(String[] args) {
    Test testObj = new Test();
    Test2 test2Obj = new Test2();
    testObj.test();
    testObj.check();
    test2Obj.test2();
  }
}

Output

[item]
[]

In your main method, you call the method that handles adding operation yet you do not call any add methods in the second class and in your main method.

 testObj.test();
 testObj.check();

This one shows that you add an item into the arraylist and show it. But in the second class you do not add anything but calling it. Therefore there is no way to show any element from that method. What has should be done is that you just need to call the adding method inside of the second class and then try to use the display method.

In java Class level variables are Object associated until unless they are not declared static.

By means of Object associated is that when a object is initialized with new keyword in Java all Object will be having it's own memory and own class variables.

In your case inside main method when you create a Object of Test class and when you create a another test class object inside Test2 class, both will be totally independent of each other. And both will be having their own memory and own variables.

If you want that to get the updates of inventory variables from first object to be available in another object you need to declare it as static and should be initialized inside static block. Static variables are shared across all objects of class. As below:

static ArrayList<String> inventory;

static {
        inventory = new ArrayList<String>();
}

You didn't call test() method in Test2 class.
To make it work change the Test2 class as follows.

import java.util.ArrayList;
public class Test2 {

Test testObj = new Test();

public void test2() {
  testObj.test();
  System.out.println(testObj.inventory);
}

}

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