Changing the value of a variable's reference in java

Question

I'm not sure if the title is the best, but what I want to do can be illustrated in this example

class TestClass {
    public String foo = "foo"

    public void makeFooBar() {
        String bar = foo;
        bar = "bar";

        System.out.println(foo); //should print "bar"
    }

}

This is obviously a contrived example, but it illustrates the point. I want to change the value of foo by changing the value of bar that references foo. is that posible?

You could if you would warp it, so it becomes an object. But plain field refference linking doesn't exist in java. — n247s, Dec 05 '16 at 21:21
Ok, I'll have to change my code so it doesn't require that. Thanks. — richbai90, Dec 05 '16 at 21:23

score 1 · Accepted Answer · answered Dec 05 '16 at 21:33

This could be a way if you want to update a certain value in multiple places (e.g. by using a wrapper object). Of course there are waay more fancier ways to accomplish something simular.

class TestClass {
    public Wrapper<String> foo = new Wrapper("foo");

    public void makeFooBar() {
        Wrapper<String> bar = foo;
        bar.set("bar");

        System.out.println(foo); //should print "bar"
    }

     public static class Wrappper<T>
    {
          T value;

         public Wrapper(T value)
         {
               this.value = value;
         }

         public T get() { return this.value; }
         public void set(T newValue) { this.value = newValue; }
         @override
         public String toString() { return value.toString(); }
    }
}

Basically any primitive type cannot be passed by reference. Althoug String is technically not a primitive type, java does treat it a bit more special. (Reading upon Internal Stringpool would give you a nice insight. In this page there is a nice explanation including some visual examples: http://www.journaldev.com/797/what-is-java-string-pool)

Changing the value of a variable's reference in java

1 Answers1