java.lang Package

java.lang Package

java.lang is automatically imported into all programs. It contains classes and interfaces that are fundamental to virtually all of Java programming. It is Java’s most widely used package.

java.lang includes the following classes:

Boolea	Byte	ThreadGroup
Long	StrictMath	RuntimePermission
StackTraceElement	Object	Process
Math	StringBuffer	Runtime
Number String	Compiler	ThreadLocal (Java 2)
Character	Double	SecurityManager
Class	Float	Integer
ClassLoader	Thread	Short
	Throwable	Void

            

java.lang also defines the following interfaces:

 Cloneable           Comparable          Runnable    CharSequence

There is one special class, Object, defined by Java. All other classes are subclasses of Object. That is, Object is a superclass of all other classes. This means that a reference variable of type Object can refer to an object of any other class.

Since arrays are implemented as classes, a variable of type Object can also refer to any array.

Object defines the following methods, which means that they are available in every object.

Object clone( ) throws CloneNotSupportedException

Creates a new object that is the same as the invoking object.

boolean equals(Object object)

Returns true if the invoking object is equivalent to object.

void finalize( ) throws Throwable

Default finalize( ) method. This is usually overridden by subclasses.

final Class getClass( )

Obtains a Class object that describes the invoking object.

int hashCode( )

Returns the hash code associated with the  invoking object.

final void notify( )

Resumes execution of a thread waiting on the invoking object.

final void notifyAll( )

Resumes execution of all threads waiting on the invoking object.

String toString( )

Returns a string that describes the object.

final void wait( )throws InterruptedException

Waits on another thread of execution.

final void wait(long milliseconds) throws InterruptedException

Waits up to the specified number of milliseconds on another thread of execution.

final void wait(long milliseconds,int nanoseconds) throws InterruptedException

Waits up to the specified number of milliseconds plus nanoseconds on another thread of execution

The clone( ) method generates a duplicate copy of the object on which it is called. Only classes that implement the Cloneable interface can be cloned. The Cloneable interface defines no members. It is used to indicate that a class allows a bitwise copy of an object (that is, a clone) to be made. If you try to call clone( ) on a class that does not implement Cloneable, a CloneNotSupportedException is thrown. When a clone is made, the constructor for the object being cloned is not called. A clone is simply an exact copy of the original.Cloning is a potentially dangerous action, because it can cause unintended side effects.

Posted By : Ruchita Pandya