Question: I saw [this question](https://stackoverflow.com/questions/2327916/operator-in-java) a few minutes ago, and decided to take a look in the java String class to check if there was some overloading for the `+` operator.

I couldn't find anything, but I know I can do this

```
String ab = "ab";
String cd = "cd";
String both = ab + cd; //both = "abcd"

```

Where's that implemented?

Answer: 
It is handled by the compiler.
It's done at the language level. The Java Language Specification is [very specific about what string addition must do](http://java.sun.com/docs/books/jls/third_edition/html/expressions.html#15.18.1).