摘 要
现实世界中的很多过程都具有多条线索同时动作的特性。Java语言的一大特性就是内置对多线程的支持。多线程是指同时存在几个执行体，按几条不同的执行线索共同工作的情况，它使得编程人员可以很方便地开发出具有多线程功能、能同时处理多个任务的功能强大的应用程序。一些同时运行的线程需要共享数据，因此每个线程就必须要考虑其它与它一起共享数据的线程的状态与行为，这就是线程安全的问题。为了对Java多线程与线程安全机制进行研究与实践，特此设计一个基于Http 协议的支持多线程断点续传的下载程序。此下载程序由下载任务模块、设置模块以及系统帮助模块组成。通过Apache Jakarta Commons下的子项目HttpClient包对Http协议进行支持，从而下载服务器端的资源。程序提供多线程断点续传功能，在完成下载过程中使用多线程技术可以较大幅度地提高下载的速度。
关键词：多线程；线程安全；断点续传
The Practice of Java Multithreading and Thread Security---- Download Tool with Broken/Resume Function based on http
Abstract
In real world, many processes have the characteristic that multi-strip clue act at the same time. The Java language has a major characteristic of embedded multithread support. Multithreading is the status that exist several implementation body at the same time, according to several different clues to the implementation of the joint work, It means that programmers can easily produce more threads development functions, It can also deal with a number of tasks powerful application. Running some of the threads need to share data, So each thread must consider other with it to share the data with the state of the thread, This is the thread safety. To Java multithreading and security mechanisms to conduct research and practice, Design hereby Http agreement on the support multithreading download procedures. This download procedures comprises of downloading task module, setting module and helping system module. With Http support of HttpClient, a subproject of Apache Jakarta Commons, it can download resources coming from web server. The procedure provides the Multi-threaded broken/resume functionality, in the process of completes downloading to use the multi-thread technology can greatly boost download speed.
