Comparison between variables pointing to same Integer object

Question

The ourput of current program is "Strange". But the both the variables share the same reference why are second and thrid comparison not true.

Integer a;
Integer b;
a = new Integer(2);
b = a;
if(b == a) {
    System.out.println("Strange");
}
a++;
if(b == a) {
    System.out.println("Stranger");
}
a--;
if(b == a) {
    System.out.println("Strangest");
}

Output: Strange

Answer 1

That's the artifact of autoboxing and a fact that Integer is immutable in Java.

The a++ and a-- are translated to roughly this.

int intA = a.getInt( );
intA++;
a = Integer.valueOf( intA ); // this is a reference different from b

Answer 2

• Strage - it's obvious, the two variables point to the same object

• not Stranger because of autoboxing. Integer is immutable, so each operation on it creates a new instance.

• not Strangest, because of the previous point, and because you have used new Integer(..) which ignores the cache that is used for the byte range. If you use Integer.valueOf(2) initially, then the cached Integers will be used and Strangest will also be printed.