在程序运行时,经常需要输入一些数据,数据输入的正确与否影响到程序的正常运行.因此,有必要对输入的数据进行检验.过滤掉不合法的数据.-in running, often need to import some data data input correct or not affect the normal operation procedures. Therefore, it is necessary to input data for examination. do not filter out legitimate data.