How do I modify private final String variable?

Question

public class x {
    private final String a;

    public void x() {
        a = "Hi";
        System.out.println(a);
    }
}

private final String a; <- this line is showing error that 'a' is not initialized.

I tried private final String a = "";

And a = "Hi";

Then it says I cannot assign a value to final variable.

How do I modify or assign new value to final String in another method?

A final variable cannot be modified. If you want to modify it, remove the final keyword. — Alexandre Cartapanis, Apr 05 '21 at 06:51
There is a possibility using reflection, but it is definitively a bad idea, have a look at https://stackoverflow.com/questions/3301635/change-private-static-final-field-using-java-reflection if you are really interested in this. But again, IT IS A BAD IDEA. — Alexandre Cartapanis, Apr 05 '21 at 06:58

CryptoFool · Answer 1 · 2021-04-05T06:57:15.570

You have an unwanted keyword "void" in there such that what you think is your constructor is actually a function definition. Just remove the void and all will be well:

public class x {
    private final String a;

    public x() {
        a = "Hi";
        System.out.println(a);
    }
}

As you see, you can set a final variable in a constructor if you didn't give it a value when you defined it.

You talk about modifying a in another method. You can't do that, as others have pointed out in the comments. That's the whole point of final. It declares that the value of a will be set once and will never change once set.

score 0 · Answer 2 · answered Apr 05 '21 at 06:50

0

You can't modify a final value, so if you want to add "Hi" as a string to that final string you should initialize it like: private final String a = "Hi";

or if you want to modify it later you have to remove final.

answered Apr 05 '21 at 06:50

Abdelrhman Ahmed

55
1
8

score 0 · Answer 3 · answered Apr 05 '21 at 06:51

For the final static variable, it is compulsory that you should perform initialization before class loading completion. You can initialize a final static variable at the time of declaration or inside the static block.

class Test {
    final static int x = 10;
    public static void main(String[] args)
    {
        System.out.println(x);
    }
}

OR in static block.

class Test {
    final static int x;
    static
    {
        x = 10;
    }
    public static void main(String[] args)
    {
        System.out.println(x);
    }
}

How do I modify private final String variable?

3 Answers3