Compiling

IntelliJ IDEA uses the built-in compiler (Javac) from Java Development Kit for compiling java source files.
The compiler is found in the JDK assigned to the project.  If the project has no JDK is assigned, a warning message will be displayed when trying to launch the compiler.
The settings from project properties such as the sourcepath, classpath and output path are passed to the compiler.

IDEA parses the output from the compiler and displays it in a convenient form in the message window, letting you navigate to the source of the problem whenever possible.

To navigate to an error in the source code, press F4 on the error node in Message View.

There are three basic types of compilation available in IDEA:

Compile file or package

Can be called with Ctrl-Shift-F9 on any file or package. When called from the editor, compiles the currently open file.

Compile Modified

Compiles all source files that have been modified since the last compilation. Can be called with Ctrl-F9.

Compile Project

Compiles all source files in the project.