为一个字节或字符数组或串计算md5值，内部只创建一个数组，节省分配时间，节省内存 完全是static方法，线程安全 注意对返回值的处理，见注释-for a byte array or character string or md5 value calculation, only to create an internal array, saving time allocated to save memory is completely static method, thread-safe att

银行家算法，实现了进程资源分配的安全性检测，对进程资源分配的模拟，使进程不处于不安全状态。-Banker' s algorithm, the allocation of resources to achieve the process safety testing, the simulation of resource allocation process, so that the process is not in safe condition.