Online Hibernate Training just in Rs. 1000

One week online training in Hibernate ORM framework. Learn Hibernate Framework and enhance your skills. Best Online Hibernate training at 90% discount. Join Now!! Offer is valid Only for limited Period!!! Online Training

Java ClassPath

What is PATH and CLASSPATH variables?


How to convert String Date to Timestamp in Java? Best Java Tutorial for Beginners Read user input in Java using Scanner Java Programming Examples Read file line by line in Java 8 What are the benefits of learning Java Programming? A brief history and future of Java programming language Importance of Java for Mobile Application Development How To Become A Good Software Developer? Learn Java Programming for beginners 5 Reasons Java is Still a Great Language to Boost Your Career Prospect as a Programmer How to learn Java with no programming experience? How to learn Java? What are Classes and Interfaces in Java? Converting a String to Integer in Java How to check if a string exists in a string in JavaScript? Installing JDK 8 on Windows 10 and configuring the settings Video Tutorial of reading file in Java 9 Invincible Reasons to learn Java New to Java programming Java Programming Tips, Articles and Notes How to download JDK 1.6? Encapsulation in Java Programming How to format number in Java? Generics Example Program in Java Java 9 Features Java 9 Tutorial, news and examples How to read content of JPEG file in Java? Image Processing Tutorials in Java Programming Language Introduction to Java Technology Java 8 Consumer Interface with forEach Loop Introduction to Generics in Java Java 8 consumer class(interface) example Oracle Launches Project Valhalla for Java How to read properties file in Java? How to add JDK 8 support in Eclipse? Java 8: Java 8 is officially released and it can be downloaded How to Invoke method using Reflection API of Java? First Lambda Expressions in Java Java 8 expected release date Lambda Expressions example in Eclipse JDK 8 Release Candidates Available Lambda Calculus Lambda Expression in Java 8 How to learn Java easily? Java made easy Oracle to release Java 8 in March 2014 Object Oriented Programming in Java Java Training Free Java beginners Course

Java ClassPath


Question: What is the meaning of PATH and CLASSPATH ? How it is set in environment variable?.

ANS:- Significance of searching class path

Java is an OOP language. In java programming language for compiling the program we use the compiler that converts the source code into the byte code after that, that byte code is interpreted by JVM that converts the bytecode into the machine independent code.  In java how the Java compiler and the JVM use the class search path to locate classes when they are referenced by other Java code. Searching class  path is important for all Java developers.Many  development tools have their own ways of manipulating the class path, which vary from product to product.For doing this we will use only simple command-line tools to carry out the compile operations. No difference, between the way that the Java compiler searches for classes, and the way that the JVM does it at run time. The compiler has the ability to compile classes from source code, where the JVM does not.  We will use the compiler, but similar issues apply at run time.

Searching of multiple class directories

  • javac(compiler)search the files in only one directory at a time.
  • But,  class search path will contain numerous directories and JAR archives. The -classpath option to javac and java allows multiple entries to be specified, but  the syntax is  different for Unix and Windows systems.

For Unix  like this

javac -classpath dir1:dir2:dir3 ...

For Windows like this 

javac -classpath dir1;dir2;dir3 ...

The difference is that Windows uses the colon (:) character as part of a filename, so it can't be used as a filename separator. Naturally the directory separator character is different as well: forward slash (/) for Unix and backslash (\) for Windows.

( I ). For running a simple program we need to set the  java path  on command prompt(for temporary )& in Environment variable using PATH variable  & CLASSPATH variable :

PATH variable 

In JDK the PATH variable contains directories where binary files (e.g. EXE files in Windows) will be looked for.We set the PATH variables like this i.e path C:\Java\jdk1.6.0_03\bin 

(i)on command prompt

C:\>set path=%path;C:\Java\jdk1.6.0_03\bin%

When you open a command prompt and type "javac", you're supposed to have the "bin" directory of your sdk into the PATH, otherwise you'll get an infamous "Command not found" error message.


In JDK the CLASSPATH contains directories (or JAR files), from where your java compiler/runtime will look for .class files (and some others). For example, "java Hello.class" will not work unless you set the directory (or JAR file) Hello.class is in, into your CLASSPATH.
i.e.classpath  C:\Java\jdk1.6.0_03\lib

For setting CLASSPATH using command prompt 

Java class path can be set using either the -classpath option when calling an SDK tool (the preferred method) or by setting the CLASSPATH environment variable. The -classpath option is preferred because you can set it individually for each application without affecting other applications and without other applications modifying its value.

(ii)on command prompt 

C:\>set classpath=%classpath;C:\Java\jdk1.6.0_03\lib%

JARs on the classpath

Java compiler and run-time can search for classes not only in separate files, but also in `JAR' archives. A JAR file can maintain its own directory structure, and Java follows exactly the same rules as for searching in ordinary directories. Specifically, `directory name = package name'. Because a JAR is itself a directory, to include a JAR file in the class search path, the path must reference the JAR itself, not the directory that contains the JAR. This is a very common error. Suppose I have a JAR jarclasses.jar in directory /jarclasses. The Java compiler look for classes in this jar, we need to specify:

javac -classpath /jarclasses/jarclasses.jar ...

and not merely the directory jarclasses.

For the CLASSPATH  use  CLASSPATH Environment Variable 

In java programming language we use the following packages such as*;  java. util.*;These  packages are  just a set of classes, you will want to store them in one place, separate from the directory where you are developing your program. Sometimes these libraries have a set of files stored in a single jar file ( with a .jar extension). From where  the Java compiler and run programs must be able to find any of these. This is done for command line use of Java and for some editors and IDEs by setting an environment variable called CLASSPATH. For  Windows, the CLASSPATH environment variable should look like this :


At the end " . "  includes the current directory in the search for classes. 

  • Suppose we have a directory MyJavaLib on the C-drive that contains some utility classes or the directories that correspond to some packages. This  is the part before the first semi-colon. 
  • Second part indicates that we have some classes stored in a file myutils.jar 
  • Third part indicates that we have a jar file blackboxclasses.jar. 

Finally, after the last semi-colon we have the period( . ), indicating that the current directory is on the CLASSPATH. If some things are stored in directories that are subdirectories, the complete path, starting with "c:\" should be in the CLASSPATH.

(2)  For  setting CLASSPATH & PATH variable  in environment variable by using the following steps:

(i) right click on my computer icon on desktop

(ii) click on properties

(iii) click on advanced

(iv) click on  Environment variables

(v)  system varables  click on  new

(vi) in ( variable name) write ----- path

in ( variable value)  paste the path till bin directory i.e.------- c:\java\jdk1.6.0_03\bin click on ok

(vii)  in system varables again click on  new

(viii) in ( variable name) write ----- classpath

in ( variable value)  paste the path till lib directory i.e.------- c:\java\jdk1.6.0_03\lib  click on ok

(ix) after finished click on ok

(x) finished click on ok

How to set System Classpath :

Java class path is set for including the various files during program execution & compilation.After setting class search path on the javac command line, we set `system' class path. This  class path  will be used by both the Java compiler and the JVM . In both Unix and Windows systems, this is done by setting an environment variable. For example, in Linux with the bash shell:

CLASSPATH=/jarclasses/jarclasses.jar;export CLASSPATH 

for Windows:

set CLASSPATH=c:\jarclasses\jarclasses.jar

We use this procedure for setting  short-term changes to the system CLASSPATH, but if you want these changes to be persistent you will need to arrange this yourself.For different - 2 system this path  is different . On a Linux system, we  put the commands in the file .bashrc in my home directory. On Windows 2000/NT there is a `Control Panel' page for this.

Setting the system CLASSPATH is a useful procedure if you have JARs full of classes that you use all the time.


Share on Google+Share on Google+

Java ClassPath

Posted on: February 16, 2005 If you enjoyed this post then why not add us on Google+? Add us to your Circles



Discuss: Java ClassPath   View All Comments

Post your Comment

Your Name (*) :
Your Email :
Subject (*):
Your Comment (*):
  Reload Image
prabhat ranjan
December 25, 2011
difficulty in setting of path of java.

Hi I have window7 operating system.and i have installed jdk-7u2-windows-x64.exe for java program. But i have a problem to set path of java. and also how to run java program.
vinayaka D J
January 9, 2012
unable to execute jar command

i am trying to execute jar command but its showing command not found what to do
Sunil Sharma
February 1, 2012
How to set the class path.

Thanks to this services for java.
Pradeep Patel
February 18, 2012
Facing problem to set the classpath in java

Hello Sir I'm Pradeep Patel facing problem to set path and classpath for java programs
March 3, 2012

i am getting noclassfound error while runtime
June 29, 2012

I have set the path and classpath in environment variables.eventhough iam getting the error like javac:file not usage java:<options> <source files> please rectify my mistake if any
September 28, 2012

My problem is the recoruse file is available in one context (say aa), I'm trying to load the same using ResourceBundle from another context (say bb). But always I get MissingResourceException exception. But it works well when I put the properties file under bb context I think I can use the solution that you mentioned in this post for the time being. But I'm searching for a solution so that I can use ResourceBundle(since the property file is for i18n purposes). Any way thanks dude it is indeed a good post.
abhishek kumar
November 2, 2012
how to set classpath temporary in java

two different folder having same package and same class name
July 31, 2013
Java Class path

Its very simple and Working fine .. Thanks