In Java, what is the difference between the following declarations?

Question

Considering Java. How are these 2 different and why?

public void languageChecks() {
    Integer a = 5;
    Integer b = new Integer(5);

    change(a); // a doesn't get incremented. value is 5
    change(b); // b does. value is now 6
}

public void change(Integer a) {
    a++;
}

Answer 1

The only difference is that

Integer b = new Integer(5);

guarantees a new object is created. The first will use an instance from a cache (see Integer.valueOf()).

Both are immutable and the references to both are passed by value (as is everything in Java). So change() has no effect on either.