how to pass an object by reference in java and changing the object vaules?

Question

I wrote a code for changing values of list by function:

package test3;
import unit4.collectionsLib.*;
public class main {

    public static void change (Node<Integer>first) {
        first = new Node<Integer>(12,first);
    }
    public static void main(String[] args) {
        Node<Integer> first = new Node<Integer>(1);
        first = new Node<Integer>(2,first);
        first = new Node<Integer>(3,first);
        Node<Integer> pos = first;
        while (pos!=null) {
            System.out.print(pos.getInfo()+"->");
            pos = pos.getNext();
        }
        System.out.println();
        change(first);
        pos = first;
        while (pos!=null) {
            System.out.print(pos.getInfo()+"->");
            pos = pos.getNext();
        }               
    }        
}

the output is :

  3->2->1->
3->2->1->

How do I pass an object in the function for changing the list?

so what can I do for that? and how does it work? is ts duplicate the object in the function? — Shemesh, Dec 27 '17 at 09:52
You would need to wrap the `first` reference in its own object with a getter and setter for the reference. — Jim Garrison, Dec 27 '17 at 09:53
@Idan .. again, you can't. you can have your method return the Node it has internally, and re-assign your original variable to it. — Stultuske, Dec 27 '17 at 09:53

score 0 · Accepted Answer · edited Dec 27 '17 at 10:57

Java is always pass by value but you can do something like this.

public class main {

    public static Node<Integer> change(Node<Integer> first)
    {
        return new Node<Integer>(12,first);
    }
    public static void main(String[] args) {
        Node<Integer> first = new Node<Integer>(1);
        first = new Node<Integer>(2,first);
        first = new Node<Integer>(3,first);
        Node <Integer>pos = first;
        while (pos!=null){
            System.out.print(pos.getInfo()+"->");
            pos = pos.getNext();
        }
        System.out.println();
        pos = change(first);
        while (pos!=null){
            System.out.print(pos.getInfo()+"->");
            pos = pos.getNext();
        }

    }

}

In your change() method, you forgot the return statement ;-). — Ralf Kleberhoff, Dec 27 '17 at 10:18

how to pass an object by reference in java and changing the object vaules?

1 Answers1