How to use a function in a jar file in another java file?

Hi,

I need to use a some function which is already there in a jar file in another java. could you please post one code showing on how to do that?

for example,

Consider a jar file created from a java file in which only one constructor is there say SHA (String message).

I need to use this SHA method in another java file.

How to import the jar file to the existing java file? import .....

thanks,

Ashwin