pass by reference in java

1// my class
2class my_number {
3  // public member variable
4  public int number;
5
6  // default constructor
7  public my_number()
8  {
9    number = 1;
10  }
11}
12// driver function
13class Main{
14  public static void main (String [] arguments)
15  {
16    // creating object
17    my_number object = new my_number();
18
19    // printing before update
20    System.out.println("number = " + object.number);
21    // update function called.
22    update(object);
23    //printing after update.
24    System.out.println("number = " + object.number);
25  } 
26  // update function.
27    public static void update( my_number obj ){ 
28    // increments number variable.       
29    obj.number++;  
30    }
31}