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Effectively final code

public void say() {

    String b = "222"; // effectively final b

    class A {

        public A(String c) {
            b = "123"; // error
        }

    }

    b = "123"; // success; if b is final, it is an error

}

Is there a more detailed difference?

Ivan
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郭牧野
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  • You just answered your own question. – Salem Aug 25 '17 at 09:25
  • effectively final is a variable where you never change its value in the entire execution of the program, whereas final is explictly specify the variable with final keyword telling the compiler not to change – HJK Aug 25 '17 at 09:26

1 Answers1

0

If your variable is affected after being declared (e.g. anytime you write "b = "123") then it is not effectively final.

In inner class or nested class (such as your class A), you can only reference variable from the outer scope (such as b) that are effectively final.

The same restriction applies to constructs that are derived from nested classes such as lambdas.

Declaring a variable with the "final" keyword is a convenient way to be sure that you variable is effectively final.

stanislas Pocthier
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