Library Classes

This tutorial would cover package java.lang which provides classes that are fundamental to the design of the Java programming language. The most important classes are Object, which is the root of the class hierarchy, and Class, instances of which represent classes at run time.
Here is the list of classes of ackage java.lang. These classes are very important to know for a Java programmer. Click a class link to know more detail about that class. For a further drill, you can refer standard Java documentation.

SN	Methods with Description
1	Boolean Boolean
2	Byte The Byte class wraps a value of primitive type byte in an object.
3	Character The Character class wraps a value of the primitive type char in an object.
4	Class Instances of the class Class represent classes and interfaces in a running Java application.
5	ClassLoader A class loader is an object that is responsible for loading classes.
6	Compiler The Compiler class is provided to support Java-to-native-code compilers and related services.
7	Double The Double class wraps a value of the primitive type double in an object.
8	Float The Float class wraps a value of primitive type float in an object.
9	Integer The Integer class wraps a value of the primitive type int in an object.
10	Long The Long class wraps a value of the primitive type long in an object.
11	Math The class Math contains methods for performing basic numeric operations such as the elementary exponential, logarithm, square root, and trigonometric functions.
12	Number The abstract class Number is the superclass of classes BigDecimal, BigInteger, Byte, Double, Float, Integer, Long, and Short.
13	Object Class Object is the root of the class hierarchy.
14	Package Package objects contain version information about the implementation and specification of a Java package.
15	Process The Runtime.exec methods create a native process and return an instance of a subclass of Process that can be used to control the process and obtain information about it.
16	Runtime Every Java application has a single instance of class Runtime that allows the application to interface with the environment in which the application is running.
17	RuntimePermission This class is for runtime permissions.
18	SecurityManager The security manager is a class that allows applications to implement a security policy.
19	Short The Short class wraps a value of primitive type short in an object.
20	StackTraceElement An element in a stack trace, as returned by Throwable.getStackTrace().
21	StrictMath The class StrictMath contains methods for performing basic numeric operations such as the elementary exponential, logarithm, square root, and trigonometric functions.
22	String The String class represents character strings.
23	StringBuffer A string buffer implements a mutable sequence of characters.
24	System The System class contains several useful class fields and methods.
25	Thread A thread is a thread of execution in a program.
26	ThreadGroup A thread group represents a set of threads.
27	ThreadLocal This class provides thread-local variables.
28	Throwable The Throwable class is the superclass of all errors and exceptions in the Java language.
29	Void The Void class is an uninstantiable placeholder class to hold a reference to the Class object representing the Java keyword void.