java pass by reference

i understood java always pass arguments by pass by value so that the original value does not change......

but i want to know how we change the value and make it effect the original value by passing an object..... how is the basic code to do this??

and is it necessary that evry time i poass a object to a method my my original value will get effected??? is my following code correct when i want to make the changes permanently....what is the mistake..

public class arr1 { int total; arr1(int total) { this.total=total; } public void count(arr1 s1,int total) {

s1.total=s1.total+4;    
System.out.println("out  "+s1.total);
}

}

class studentk { public static void main(String[] args) { int total=500; arr1 s= new arr1(total);

  System.out.println("mark 1: "+total);
  s.count(s,total);
  System.out.println("mark 2: "+total);

}

}