[sreque]

I disagree with this to some extent. Unit tests are a pretty good poor-mans REPL in languages that don't have REPLs. For instance, I've seen people write fake unit tests to do things like query a database for analysis purposes; it was just the fastest way they could come up with to do the exploratory work. What makes a unit test a good poor-mans REPL in a language like java with an IDE is:

* Java IDEs, especially eclipse, are amazing at fast, incremental compilation. You make one change, and then only recompile what you need to.

* Java has no relatively expensive link stage like C++, C, even C# to a lesser extent, when running tests from an IDE. Your IDE can run your unit tests and also be smart enough to only load the classes it needs to run the test.

Most dynamic languages already have a REPL, so the technique of using unit tests for exploratory work isn't necessary, but I think it's very useful for Java at least.

[stcredzero]

Unit tests are a pretty good poor-mans REPL in languages that don't have REPLs.

Java IDEs, especially eclipse, are amazing at fast, incremental compilation. You make one change, and then only recompile what you need to.

I always found this lugubrious compared to the experience in many Smalltalks. The Java vs. Smalltalk USENET flame wars in the 90's were partly motivated by the downgrade in developer UX caused by the taking of the Smalltalk runtime model and deliberately crippling it.

Granted, Java has made amazing progress since then, as have IDEs generally. Is there a non-Smalltalk environment that lets one "code in the debugger" to the same extent as Smalltalk? I know of Clojure and the kind of experience shown with LightTable. (To elaborate, to "code in the debugger" in Smalltalk is very nimble and powerful. It's kind of like the turn-based version of LightTable but with pausing in the debugger and manual tinkering/time-travel with the context stack.)

[sreque]

The JVM is less dynamic in its ability to reload code, but the payoff is that java code can be 10-100x faster than smalltalk code. I personally think the performance gain is worth it. Hotspot has some limited support for hot code reloading, which is a pre-requisite to being able to "code in your debugger", but it's limited enough that I don't bother with it. Alternatively, you can code in a dynamic language on the JVM such as JRuby or Clojure and have full support for "coding in the debugger". These languages are also a lot slower than Java.

[skybrian]

We are talking Go here, which has a fast compiler. The IDE integration isn't always as good as Java, though.

[_ivvf]

Go has a fast compiler but to my knowledge has zero support for incremental compilation. It has to recompile the entire project, transitively with all its dependencies, before you can run your code modification. I haven't code in go, but IMO this does not scale well as projects grow in size.

[stcredzero]

I find GoLand to be quite good.

[sitkack]

Seconded, GoLand isn't just quite good, it is phenomenal. If you aren't running it, you need to have a compelling reason.

https://www.jetbrains.com/go/