The standard Java libraries fail to provide enough methods for
manipulation of its core classes. Apache Commons Lang provides these
extra methods.

Lang provides a host of helper utilities for the java.lang API,
notably String manipulation methods, basic numerical methods, object
reflection, concurrency, creation and serialization and System
properties. Additionally it contains basic enhancements to
java.util.Date and a series of utilities dedicated to help with
building methods, such as hashCode, toString and equals.

WWW: http://commons.apache.org/proper/commons-lang/