Why can method reference use non-final variables?

Question

I had some confusion about inner classes and lambda expression, and I tried to ask a question about that, but then another doubt arose, and It\'s probable better posting ano

Answer 1

Your second example is simply not a lambda expression. It's a method reference. In this particular case, it chooses a method from a particular object, which is currently referenced by the variable one. But the reference is to the object, not to the variable one.

This is the same as the classical Java case:

One one = new One();
One two = one;
one = new One();

two.bar();

So what if one changed? two references the object that one used to be, and can access its method.

Your first example, on the other hand, is an anonymous class, which is a classical Java structure that can refer to local variables around it. The code refers to the actual variable one, not the object to which it refers. This is restricted for the reasons that Jon mentioned in the answer you referred to. Note that the change in Java 8 is merely that the variable has to be effectively final. That is, it still can't be changed after initialization. The compiler simply became sophisticated enough to determine which cases will not be confusing even when the final modifier is not explicitly used.