无法分配最终的局部变量标记，因为它是在封闭类型中定义的

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(","));