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What does dollar sign mean in generated variable names during debugging Java in InteliJ IDEA ? Is it a closure?

What does dollar sign mean in variable names during debugging Java in InteliJ ? Is it a closure ? Please see the image and code snippet below.

Here is part of the Stream class:

public final Listener listen(final Handler<A> action) {
    return listen_(Node.NULL, new TransactionHandler<A>() {
        public void run(Transaction trans2, A a) {

I suspect that the $1 in Stream$1@915 refers to the closure created in the method above. I am not sure though. Can someone confirm this ? Or if that is not the case, explain what the dollar sign means in this generated name ?

The code is taken from the Sodium Functional Reactive library which I am trying understand how it works.

enter image description here

like image 617
jhegedus Avatar asked Mar 18 '23 02:03


1 Answers

It's a reference to the anonymous inner class thats generated by this closure like construct. In general, inner classes are compiled and the class file name will be yourClassName$yourInnerClassName. In the case of an anonymous inner class declaration, since you don't name it explicitly, it will appear as a generated name using numbers. Perhaps this article will help?

like image 157
Amir Afghani Avatar answered Apr 06 '23 00:04

Amir Afghani