Question

Possible Duplicate:
Wrapper class and == operator

Saw this code in a website when i was learning about autoboxing..

Integer i1 = 1;  
Integer i2 = 1;  
// true 
System.out.println(i1 == i2);  


Integer i3 = -200;  
Integer i4 = -200;  
// false
System.out.println(i3 == i4);   

I can understand why the 2nd comparison gives false (its comparing references). But why is it giving true for the first one ?

Answer 1

Because the first several Integer objects (from -128 to 127, inclusive, to be precise) are cached and reused by the JVM, so i1 and i2 are references to the same physical object.

This is also true to Long, Short and Byte btw. See this article for a more detailed explanation.