java - passing a double value by reference

Question

how can I pass a double value by reference in java?

example:

Double a = 3.0;
Double b = a;
System.out.println(\"a: \"+a+\" b: \"+b);
a = 5.0;
System.         


        

Answer 1

The wrapper types are immutable in Java. Once they are created, their value cannot be changed (except via reflection magic ofcourse). Why are you trying to do what you're doing?

Edit: Just to elaborate, when you set:

a = 5.0;

What actually ends up happening is something like:

a = new Double(5.0);

If double were mutable, you could have done something like

a.setValue(5.0);// this would have worked for mutable objects, but not in this case

You can of course write your own class, but there are a lot of pitfalls here, so it's best to explain you're goal