利用内存映射原理实现的同时只能运行一个实例的例子，并可以自动激活最后运行的一个实例，你也可以指定最多可以同时运行实例的数量-Realize the principle of the use of memory-mapped at the same time can only run one instance of the example, and can automatically activate an instance of the last run, you can also specify the maximum number of instances running at the same time