What are the advantages of using an ExecutorService?

Question

What is the advantage of using ExecutorService over running threads passing a Runnable into the Thread constructor?

Answer 1

Prior to java 1.5 version, Thread/Runnable was designed for two separate services

1. Unit of work
2. Execution of that unit of work

ExecutorService decouples those two services by designating Runnable/Callable as unit of work and Executor as a mechanism to execute ( with lifecycling) the unit of work