As Svish and others pointed out it it's call by value, not by reference in Java. Since you have no pointers in Java you need some kind of holder object to really swap values this way. For example:
static void swap(AtomicReference a, AtomicReference b) {
Integer c = a.get();
a.set(b.get());
b.set(c);
}
public static void main(String[] args) {
AtomicReference a = new AtomicReference(1);
AtomicReference b = new AtomicReference(2);
System.out.println("a = " + a);
System.out.println("b = " + b);
swap(a, b);
System.out.println("a = " + a);
System.out.println("b = " + b);
}
