首先这个题目要用到递归，递归就是自己调用自己的意思，直到条件不满足。            设计一个f方法            具体代码如下：                    public int f(int n){                        if(n>1){                            return n*f(n-1);}                            else{                                return 1;                            }                    }                    当传入参数为5时，                 5>1 返回5*f(4)                    f(4)则调用f方法传入参数为4   4>1 返回4*f(3)                                                        同理  3>1 返回3*f(2)                                                                    2>1 返回2*f(1)                                                                 1=1 返回1                    最后返回值为：5*4*3*2*1                     只要输出即可求出5！。