Question

public class AAA {
    public static void main(String[] args) {
        Integer bbb, aaa = new Integer(5);
        System.out.print(aaa);
        bbb = aaa;
        System.out.print(bbb);
        aaa = 4;  
        System.out.print(aaa);
        System.out.print(bbb);
    }
}

Why as a result I see: 5545 instead of 5544?

*java version “1.7.0_10”

Thank to all, I understood my mistake.

Answer 1

public class AAA {
    public static void main(String[] args) {
        Integer bbb, aaa = new Integer(5);
        System.out.print(aaa);
        bbb = aaa;

The above line assigns bbb and aaa to point to the same object.

        System.out.print(bbb);
        aaa = 4;  

Now aaa points to a new object (which is created invisibly by autoboxing). This does not change the value of the original object which bbb still points to. Note that Integer is immutable. This means it is impossible to change the value of an Integer object. You can only a create new Integer object with a different value.

        System.out.print(aaa);
        System.out.print(bbb);
    }
}