Change the value of final Integer variable

Question

A final object cannot be changed, but we can set its attributes:

final MyClass object = new MyClass();
object.setAttr("something");              //<-- OK
object = someOtherObject;                 //<-- NOT OK

Is it possible to do the same with a final Integer and change its int value?

I'm asking because I call a worker:

public SomeClass myFunction(final String val1, final Integer myInt) {

    session.doWork(new Work() {
    @Override
    public void execute(...) {
        //Use and change value of myInt here
        //Using it requires it to be declared final (same reference)
    }
}

And i need to set the value of myInt inside of it.

I can declare my int inside another class, and that would work. But I wonder if this is necessary.

Solution 1

No : an Integer is immutable, just like for example String.

But you can design your own class to embed an integer and use it instead of an Integer :

public class MutableInteger {
    private int value;
    public MutableInteger(int value) {
        this.value = value;
    }
    public int getValue() {
        return value;
    }
    public void setValue(int value) {
        this.value = value;
    }
}

Solution 2

You can't because it immutable by design.

You can set the value of an int[] or Integer[] or AtomicInteger

Solution 3

You cannot change the value of final integer once assigned.. However, you can delay the assignment., i.e. : - You can only assign a final integer once.. You can do it either at the time of declaration, or in initializer block, or in constructor..

Solution 4

You could wrap your Integer in another object that is final and then 'replace' the Integer inside that wrapper object by another.

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Comments

[sheidaei]

I would have used String instead of Number, since he has used it in his example :D too picky, I know :D but a great short answer

[Benj]

You can simplify that by making value public. This is crappy but efficient. Then, you will access myMutableIntegerObj.value (e.g. from an inner class). +1 for @dystroy