Idempotent / non-idempotent operations in the Java client server implementation


I have searched for examples on idempotent and non-idempotent operations but there aren't much on them that is relevant for implementation on a java client-server system. Can you guys give me some examples of both idempotent and non-idempotent operations that can be implemented for a java client-server system, primarily for text reading and insertion?

Reading operations should generally be idempotent by nature. However, posting a text may not be. With some systems, posting a text more than once results in both getting added separately. If texts have permanent unique IDs (a new text can never reuse an older one's ID, even if the older one no longer exists), deletion by ID is also idempotent.