Question

I have the following code

class sample
{

  public void update(List l)
  {
      l = null;
  }

  public static void main (String[] args)
  {

      List m = new ArrayList();
      m.add("suresh");
      m.add("sankar");
      new sample().update(m);
      System.out.println(m);
  }
}

The answer will be {[“suresh,”sankar”]}. The m is a pointer to the arraylist object, it contains an memory address value (for ex consider 0xf34 ). when we pass m to update method ,the local variable l will be set to 0xf34 that points to arraylist object in memory .when we set null to this variable l , the memory address replaces the arraylist with null ,hence the variable m should also refer null.am i right.please help.

Answer 1

No, the compiler has it right. 🙂

The parameter l contains a reference to the ArrayList object assigned to m. l gets updated to null, and indeed any later use of lwithin the update() method would see it as null. But l is a separate variable that has scope only within that method — it’s not linked to m in any way (other than the fact that they originally contained references to the same object).