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wrappers

rakhee gupta
Ranch Hand

Joined: May 01, 2008
Posts: 43
Hi,
Check the following program:

public class Temp
{

public static void main(String[] args)
{
Integer i1 = 1000;
Integer i2 = 1000;
if(i1 != i2) System.out.println("different objects i1 i2");
if(i1.equals(i2)) System.out.println("meaningfully equal i1 i2");

Integer i3 = 10;
Integer i4 = 10;
if(i3 != i4) System.out.println("different objects i3 i4");
if(i3.equals(i4)) System.out.println("meaningfully equal i3 i4");

}
}

The output is:

different objects i1 i2
meaningfully equal i1 i2
meaningfully equal i3 i4

Please clarify.Why i1 and i2 are different objects when both are Integer and have value 1000 which is in the range of int.

Thanks
marc weber
Sheriff

Joined: Aug 31, 2004
Posts: 11343

Originally posted by rakhee gupta:
...Why i1 and i2 are different objects when both are Integer and have value 1000 which is in the range of int...

To get the same reference when autoboxing, the values need to be within the range of a byte.

JLS 5.1.7 - Boxing Conversion...
If the value p being boxed is true, false, a byte, a char in the range \u0000 to \u007f, or an int or short number between -128 and 127, then let r1 and r2 be the results of any two boxing conversions of p. It is always the case that r1 == r2.

My bold.


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