The Java Tutorials have been written for JDK 8. Examples and practices described in this page don't take advantage of improvements introduced in later releases and might use technology no longer available.
See Dev.java for updated tutorials taking advantage of the latest releases.
See Java Language Changes for a summary of updated language features in Java SE 9 and subsequent releases.
See JDK Release Notes for information about new features, enhancements, and removed or deprecated options for all JDK releases.
Here is the complete source code for the GenSig.java program, with some comments added. Compile and run it. Remember, you need to specify the name of a file to be signed, as in
java GenSig data
You can download and use this sample file named
data or any other file you like. The file will not be modified. It will be read so that a signature can be generated for it.
After executing the program, you should see the saved suepk (public key) and sig (signature) files.