Java stopped erroring on non-final variables in inner classes (java 8) [duplicate]

Answer 1

The variable message is effectively final. Quoting from language reference

If a variable is effectively final, adding the final modifier to its declaration will not introduce any compile-time errors.

Hence, because message reference is not changed anywhere within you inner class, the compiler treats it as effectively final.

This would have thrown error:

new Runnable() {
            @Override
            public void run() {
                message = "hey";
                System.out.println(message);
            }
        }.run();

The reason, java7 compiler throws error is because of a spec change for lambdas.

Any local variable, formal parameter, or exception parameter used but not Any local variable, formal parameter, or exception parameter used but not declared in a lambda expression must either be declared final or be effectively final (§4.12.4), or a compile-time error occurs where the use is attempted.

Anonymous Inner classes and lambdas share the same rules.