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

The Lang Component provides a host of helper utilities for the
java.lang API, notably String manipulation methods, basic
numerical methods, object reflection, creation and serialization,
and System properties. Additionally it contains an inheritable
enum type, an exception structure that supports multiple types of
nested-Exceptions and a series of utlities dedicated to help with
building methods, such as hashCode, toString and equals.

WWW: http://jakarta.apache.org/commons/lang.html