Declare final variable, but set later

Question

I know this is fairly simple topic, but I really want to wrap my head around it.

This is what I\'m trying to do, but it doesn\'t like the final modifier. Is there an

Answer 1

You can't. But you can guarantee no external object changes it if it's private and you don't have a setter for it.

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Alternatively, you can wrap the long value in another class - LazyImmutableLong. But this is a more verbose approach, and you probably don't need it (note: the class below is not thread-safe)

class LazyImmutableLong {

    private Long value;

    public void setValue(long value) {
         if (this.value != null) {
             return; // the value has already been set
         }
         this.value = value;
    }
    public long getValue() {return value;}
}

And in your activity

private LazyImmutableLong id = new LazyImmutableLong();

public void onCreate(..) {
    id.setValue(..);
}