求n的阶乘

package test;import java.math.BigDecimal;//求n的阶乘public class Factorial {public static BigDecimal one = new BigDecimal(1);//用 int或long 数字稍大就会溢出public static int calculate(int n){if(n==1) return 1;return n*calculate(n-1);}//这种方法BigDecimal能表达足够大的数字，但递归调用层次太深，最终会出现栈溢出public static BigDecimal calculate(BigDecimal n){if(n.equals(one)) return n;return n.multiply(calculate(n.subtract(one)));}//用BigDecimal 和非递归的方式可避免上述的两个问题public static BigDecimal notRecursiveCalculate(BigDecimal n){BigDecimal i = new BigDecimal(1);BigDecimal rs = new BigDecimal(1);for(; i.compareTo(n)<=0;i=i.add(one)){rs=rs.multiply(i);}return rs;}/** * @param args */public static void main(String[] args) {System.out.println(Factorial.calculate(11));System.out.println(Factorial.calculate(new BigDecimal(1100)).toString());System.out.println(Factorial.notRecursiveCalculate(new BigDecimal(5555)).toString());}}