Classpath importance in Java

http://javarevisited.blogspot.com/2011/01/how-classpath-work-in-java.html

IMP video tutorial for classpath in Java -> https://www.youtube.com/watch?v=o08TvSyKmpk
                                         -> https://www.youtube.com/watch?v=O8eNxELc4dE

Other Importance of classpath:

1.      Classpath in Java is an environment variable used by Java Virtual machine to locate or find 
class files in Java during class loading.

2.      You can override value of Classpath in Java defined by environment variable CLASSPATH by providing
JVM command line option –cp or –classpath while running your application.

3.      If two classes with same name exist in Java Classpath then the class which comes earlier in
Classpath will be picked by Java Virtual Machine.

4.      By default CLASSPATH in Java points to current directory denoted by "." and it will look for
any class only in current directory.

5.      When you use the -jar command line  option to run your program as an executable JAR, then the
Java CLASSPATH environment variable will be ignored, and also the -cp and -classpath switches will be ignored and In this case you can set your java classpath in the META-INF/MANIFEST.MF file by using the Class-Path attribute.

6.      In Unix of Linux Java Classpath contains names of directory with colon “:” separated , On
Windows Java Classpath will be  semi colon “;” separated while if you defined java classpath in Manifest
file those will be space separated.

7.       You can check value of classpath in java inside your application by looking at following
system property “java.class.path”  System.getProperty("java.class.path")

Class-Path attribute is used to contain classpath inside manifest file. Also make sure that your
manifest file must end with a blank line (carriage return or new line) , here is an example of java 
classpath in manifest file.

Main-Class: com.classpathexample.Demo_Classpath
Class-Path: lib/tibco.jar lib/log4j.jar

8.       It’s also important to note that path specified in manifest file is not absolute instead 
they are relative from application jar’s path. For example in above if your application jar file is 
in C:\test directory you must need a lib directory inside test and tibco.jar and log4j.jar inside that.

9.       ClassNotFoundException is an Exception and will be thrown when Java program dynamically tries
to load a particular Class at Runtime and don’t find that on Java classpath due to result
of Class.forName() or loadClass() method invocation.

10. NoClassDefFoundError comes when a particular class was present in Java Classpath during
compile time but not available during runtime on Classpath in Java.