Method-Local Inner Classes?

[Minhaj Mehmood]

Can anyone give me the example of Method-Local Inner Classes on-job(usage in real life) example?

[Deepak Bala]

I have never used one and never found the reason to use one.

I did encounter it once when maintaining some code. A programmer had used a local class to hold the values that a JDBC database call returned. These values were put into an object and used immediately. It was a pretty long method. I thought it made the method look ugly and if the class were to be used somewhere else, it would not be possible. I try to avoid method local inner classes

[Waclaw Borowiec]

I found these kind of classes useful in a scenario when I was sending a message to another part of a system and I waited for an asynchronous reply in a separate thread. The code looked somewhat like this:

    

void method(int id){
    send(new Message(id));
    class ReplyThread extends Thread {
        int id;
        ReplyThread(int id){
            this.id = id;
        }

        public void run(){
            try{
                Reply r = receiveReply();
                if (r.getId() == this.id){
                    log.info("ok");
                } else {
                    log.warn("bad id");
                }
            } catch (TimeoutException e) {
                log.error("timeout");
            }
        }
    }

    ReplyThread rt = new ReplyThread(id);
    rt.start();
}

ReplyThread is not used anywhere else bedside this method so in terms of scope there's no need for it to be declared on higher level i.e. as an inner or a top level class. Of course for someone readability can have higher priority than the narrowest possible scope.

[Minhaj Mehmood]

I see - Thanks for the code Waclaw Borowiec