Thanks bduncan and paul.
I had already taken care of the path variables. Now i had resolve the problem of compiling the source code thru DOS prompt. Actually the problem was instead of command javac HelloWorldApp.java i was issuing the command javac HelloWorldApp.Java and this J vs j was making the difference.
Also the problem which i am facing right now is that even though i being able to compile the program thru DOS prompt i could not able to make thru TEXTPAD. What i am doing in textpad, opening the same source file(which i able to compile successfully thru DOS prompt) and then trying to compile thru <Compile
Java> option which is available in the Textpad itself. but textpad also assuming this as an JAVA extension and giving the same error. Please tell me how to resolve this problem.