How can we implement Synchronous/Asynchronous method call in java (at server side).
Synchronous methods are implemented by simply calling one method after the other:
Asynchronous method calls are done using Threads, where each method (or task) you want to perform is executed in a different Thread, possibly with call backs or synchronization to communicate completion. There are a handful of tools which will make the job easier - read up on ExecutorService, Future, and CompletionService. You should also familiarize yourself with Concurrency Chapter of the Java Tutorial.