Java - Library Classes

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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 package 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.

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



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