The final local variable token cannot be assigned, since it is defined in an enclosing type

Question

I'm getting The final local variable token cannot be assigned, since it is defined in an enclosing type compilation error at the token inside the forEach and lambda . All I want to do is assign the only item in the list to token variable.

PS: I know for sure that there is only one item in the list .

    public static void main(String[] args) throws Exception {
        final StringBuilder token;
        AuthResponse authResponse = new AuthResponse();
        authResponse.getTokens().forEach(item -> {
            token.append(item.getToken());
        });
    }

If I declare token as an Instance variable there is no problem. But is there any other way to do it?

There are a few posts regarding this but I'd like to understand the resolution for this issue

EDIT : I have updated the question to have StringBuilder instead of String

Answer 1

You need to assign an instance:

StringBuilder token = new StringBuilder();

But why are you reinventing the wheel; use something like:

String tokens = new AuthResponse().getTokens().stream()
    .map(Object::toString)
    .collect(Collectors.joining(","));