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