Where TO Add A jar File

i had To include a jar file for my code
i had specified the path of the jar file in the classpath
and also tried by adding the jar file in the bin folder of jdk
but cmd is giving error can not find that package
can u say me where to specify the path of the jar and where to place the jar file

but when im doing the same by specifying the path of the jar file in cmd then its working
is thr any permanent solution
so that i don't have to give jar file the path again and again while compiling the class