通过多线程的编程实现圆周率简单计算方式，是多线程编程中较为简单的题目，但整体结构上比较易懂，是初学者学习多线程变成的入门代码。-Through a multi-threaded programming pi simple calculation method is relatively simple multi-threaded programming topics, but the overall structure is relatively easy to understand, is f