system
Given the following post, respond as if you're commenting on Reddit:
human
How can I easily differentiate between Java, C++, and C#?

How can I tell just by looking at them? What makes them different and what is it about these differences that makes them good for different tasks?
gpt
Look at the top of the file.  Typically you'll see:

* **Java:** `import ____;`
* **C/C++:** `#include<____>`
* **C#:** `using ____;`

If you don't see these, look for a `main()`/`Main()` method:

* **Java:** Takes a `String[]` or `String ...` argument
* **C/C++:** Takes a `char*[]`, `char**`, or `void` argument
* **C#:** Takes a `string[]` argument

The first difference you'll find in languages is where they can run.  Java can run on operating systems that have the Java Virtual Machine (JVM) installed.  Java compiles into "bytecode" that is interpreted during run-time by the JVM.  C/C++ can run on any operating system for which there exists a C/C++ compiler.  Most operating systems have a C/C++ compiler for them, but you have to compile separate binaries for each OS.  C# is the same way, but C# is most often run on Windows only (there is a project called Mono that is trying to change this).

Other differences include the amount of control you get (how close the language is to the hardware versus how abstract various things are).  C is pretty low-level.  C++ is a bit more abstract.  Java and C# are even more abstract than that, probably with Java being the most abstract of the two.

You might also find that speed is a determining factor, depending on the operating system and compiler.  Typically, it is believed that C/C++ is fastest with Java and C# trailing behind, but you'll find others argue that Java and C# are just as fast.

The different languages offer lots of different features.  C# has LINQ, lambdas, async/await, etc.  Java also has lambdas, but not until recently.  It also has global imports.  C++ has pointers.  There are a ton of differences.  Further, each language comes with a standard library.  The standard libraries for Java and C# are more built out than the standard library for C.  The standard library for C++ is much closer to that of C# or Java, but it still has a way to go.