说明：  When you work with a computer, you can do several things at once. You can hear music while you edit a document in a word processor and read your e-mail. This can be done because your operating system allows the concurrency of tasks. Concurrent programming is about the elements and mechanisms a platform offers to have multiple tasks or programs running at once and communicate with each other to exchange data or to synchronize with each other. Java is a concurrent platform and offers a lot of classes to execute concurrent tasks inside a Java program. With each version, Java increases the functionalities offered to programmers to facilitate the development of concurrent programs.include code