Sign Up to our social questions and Answers Engine to ask questions, answer people’s questions, and connect with other people.
Login to our social questions & Answers Engine to ask questions answer people’s questions & connect with other people.
Lost your password? Please enter your email address. You will receive a link and will create a new password via email.
Please briefly explain why you feel this question should be reported.
Please briefly explain why you feel this answer should be reported.
Please briefly explain why you feel this user should be reported.
final Object o;
List l = new ArrayList(){{
// closure over o, in lexical scope
this.add(o);
}};
why must o be declared final? why don’t other JVM languages with mutable vars have this requirement?
This is not JVM-deep, it all happens at syntactic-sugar level. The reason is that exporting a non-final var via a closure makes it vulnerable to datarace issues and, since Java was designed to be a “blue-collar” language, such a surprising change in the behavior of an otherwise tame and safe local var was deemed way too “advanced”.