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Here is a quick synopsis of some of the classes you'll find in the java.lang package:

Object

The ultimate root class of all Java classes

Class

A class that describes a Java class.

Wrapper Classes

These are:

• Boolean
• Character
• Number
  • Byte (JDK 1.1)
  • Short (JDK 1.1)
  • Integer
  • Long
  • Float
  • Double

These classes provide immutable wrappers for the primitive data types, when you wish to manipulate such types as objects -- especially to allow for their use in polymorphism.

Number is an abstract class, from which the numeric wrappers all derive. All the other classes are final classes.

String, StringBuffer

Objects that represent strings.

String is an immutable type.

StringBuffer allows its string to be changed in place.

Runtime

Contains a number of low-level methods associated with the Java run-time system.

System

Contains a number of low-level methods associated with the system.

All its methods are class methods; it may not be instantiated.

Math

Provides support for the mathematical values e and p, and defines static methods for floating point trigonometry, exponentiation, minimum, maximum, and pseudo-random number generation.

All its methods are class methods; it may not be instantiated.

Thread

Provides support for multiple threads of control running within the same Java interpreter.

Process

Defines a platform-independent interface to platform-dependent processes running externally to the Java interpreter.

Throwable, Exception, Error, and Specific Exception Classes

Defines a set of objects that may be thrown as exceptions.

This page was last modified on 02 October, 2007