javdoc.exe problems

I am working in Eclipse and want to generate javadocs for my packages. I was unable to find javadoc.exe on my JDK directory. I copied it from a friend and tried to configure it in my Eclipse. When I tried to generate docs, I got following exception:

Code:

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java.lang.NoClassDefFoundError: com/sun/tools/javadoc/Main
Exception in thread "main"

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I get the same when I try to run it from command prompt.

Please sort this for me ASAP.

Thanks in advance.