Doubt in Paramater Passing (Primitives to Wrappers)

[Suresh Rajadurai]

Hi Folks,

I have a problem in the following code:

class customer
{
	public static void main(String[] args) 
	{
		customer inst_test = new customer();
		int i1 = 2200;
		int i2 = 2200;
		int i3 = 12;
		int i4 = 12;
		Integer I3 = new Integer(2); 
		Integer I4 = new Integer(2); 
		System.out.println( I3 == I4 );
		inst_test.method( i3 , i4 );
		inst_test.method( i1 , i2 );
	}
	public void method( Integer i , Integer eii )
	{
		System.out.println(i == eii );
	}
}

When I compiled this code and ran this, the output was
false, true, false.

But I expected to be false false false. Since when the primitives are wrapped, it become different objects. Can anybody throw some light on it PLEASE.

Much appreciated.

Regards

Suresh.

[Campbell Ritchie]

It is probably to do with caching; I think, when you start instantiating Integer objects, the JVM creates a cache of small (-128 <= i < 128) values. When you "box" the 12 into an Integer, the JVM reuses the Integer(12) in the cache. So you have the same Integer(22) twice, so == returns true.

[Suresh Rajadurai]

Thank you.

[Campbell Ritchie]

You're welcome