Java不是完美的，Java的不足除了体现在运行速度上要比传统的C++慢许多之外，Java无法直接访问到操作系统底层（如系统硬件等)，为此Java使用native方法来扩展Java程序的功能。-Java is not perfect, Java in addition to the lack of speed in the run than traditional C++ Slow many outside, Java can not directly access to the underlying operating system (such as system hardware, etc.), for which Java method to expand the use of native Java program functions.