许多种类的应用程序都需要长时间操作，比如：执行一个打印任务，请求一个 Web Service 调用等。用户在这种情况下一般会去转移做其他事情来等待任务的完成，同时还希望随时可以监控任务的执行进度。 -many types of applications require prolonged use, such as : the implementation of a print job, request a so called Web Service. Users in this situat

监控系统的打印队列，采用多线程同时监控多个打印机中的打印队列。-Print queue monitoring system, using multiple threads simultaneously monitoring multiple printers in the print queue.