What does a variable being “effectively final” mean? [duplicate]

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Effectively final means that it is never changed after getting the initial value.

A simple example: 

public void myMethod() {
    int a = 1;
    System.out.println("My effectively final variable has value: " + a);
}

Here, a is not declared final, but it is considered effectively final since it is never changed.

Starting with Java 8, this can be used in the following way: 

public void myMethod() {
    int a = 1;
    Runnable r = new Runnable() {
        @Override
        public void run() {
            System.out.println("My effectively final variable has value: " + a);
        }
    };
}

In Java 7 and earlier versions, a had to be declared final to be able to be used in an local class like this, but from Java 8 it is enough that it is effectively final.

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