== with Boxing

[sandeeep shinde]

Please take a look at the code below

   public class MyClass {

 public Integer startingI;

 public static void main (String[] args){
	 new MyClass().methodA();
 }
 public void methodA() {
 Integer i = new Integer(25);
 startingI = i;
 methodB(i);
 }
 private void methodB(Integer i2) {
	 i2 = i2.intValue();

	System.out.println(i2 == startingI);
	System.out.println(i2.equals(startingI));

 }
 } 

The output produces "false true" .
If the values in the wrappers being compared are in the range -128 to 127 the == should return true.
But how does it return false here.
If I comment the statement i2 = i2.intValue(); the == returns true.
Can somebody please guide me on this?

[Embla Tingeling]

sandeeep shinde wrote:Can somebody please guide me on this?

Change this

Integer i = new Integer(25);

to this,

Integer i = 25;

If you do that, i will be assigned the unique reference associated with the 25 literal. Whenever you use the new operator a new object will be created so if you do new Integer(25) this refernce will differ from the one associated with 25.

[sandeeep shinde]

Ok. So when methodB is called the i2 has reference to same object as startingI. But when I am doing i2 = i2.intvalue ; the reference to the literal 25 is getting assigned to i2.
Am I correct?

[Embla Tingeling]

sandeeep shinde wrote:Ok. So when methodB is called the i2 has reference to same object as startingI. But when I am doing i2 = i2.intvalue ; the reference to the literal 25 is getting assigned to i2.
Am I correct?

Yes.

i2 = i2.intValue();

Whatever reference was held in i2, after the above operation i2 will refer to the unique object representing the i2.intValue() value (if it's within -128 through 127).

[sandeeep shinde]

Thanks a lot for your replies uj nossnahoj .

[Embla Tingeling]

You're wellcome.

Note that although this behavior is defined by Java it's easy to get it wrong so it's better not to write code that depends on it.