java - Comparison between variables pointing to same Integer object

Question

The output of current program is "Strange". But both the variables share the same reference. Why are the second and third comparisons 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