Checkstyle defines a set of available modules, each of which provides rules checking with a configurable level of strictness (mandatory, optional...). Each rule can raise notifications, warnings, and errors. For example, checkstyle can examine: * Javadoc comments for classes, attributes and methods; * Naming conventions of attributes and methods; * Limit of the number of function parameters, line lengths; * Presence of mandatory headers; * The use of packets imports, of classes, of scope modifiers and of instructions blocks; * The spaces between some characters; * The good practices of class construction; * Duplicated code sections;[2] * Multiple complexity measurements, among which expressions.

* An open source Java application that you can run from the command line. * A simple web application. * A RESTful API. * Efficiency. The Closure Compiler reduces the size of your JavaScript files and makes them more efficient, helping your application to load faster and reducing your bandwidth needs. * Code checking. The Closure Compiler provides warnings for illegal JavaScript and warnings for potentially dangerous operations, helping you to produce JavaScript that is less buggy and easier to maintain.