![enter image description here](https://i.stack.imgur.com/mlPQM.png)

I am trying to understand [this](https://github.com/SodiumFRP/sodium) Functional Reactive Java library by running a [test](https://github.com/SodiumFRP/sodium/blob/master/java/tests/java8/sodium/StreamTester.java) called `testSendStream` in debug mode and stepping through the code as the test executes. 

The snapshot above shows that there is an oddly named variable called `this$0`. 

Where does this name come from ? 

What does this name mean ? 

Why does this variable has this name ? 

What is the reasoning behind giving it this name? 

Surely this name does not come from the code itself, it is generated by IntelliJ or javac/java. But why ?

It is also interesting to see what happens if I mark this object by the label `Mystery Object`.

![enter image description here](https://i.stack.imgur.com/dwdJN.png)