I save my java programs in f drive.
when i open CMD to execute the program, i first use set path="c:/program files/java/jdk1.6.0_14/bin
after this i make way to f drive then to folder in which i save my java programs. The problem is that message

exception in thread main java.lang.noclassdeffounderror

and this error doesn't occur on every program. it is happening for few programs. I am just making basic java programs right now. please help me to solve this problem.

Hello,
Usually need to set the classpath. Is the java program file name identical in case to the class name in the java program?

yes it is same

I made more programs today they were running properly but the problem is happening for a particular program

Need to see the program and the command(s) issued to launch it along with a copy of the error message(s).