factorial2.java

非常典型的164个很好的java代码

/*
 * Copyright (c) 2000 David Flanagan.  All rights reserved.
 * This code is from the book Java Examples in a Nutshell, 2nd Edition.
 * It is provided AS-IS, WITHOUT ANY WARRANTY either expressed or implied.
 * You may study, use, and modify it for any non-commercial purpose.
 * You may distribute it non-commercially as long as you retain this notice.
 * For a commercial use license, or to purchase the book (recommended),
 * visit http://www.davidflanagan.com/javaexamples2.
 */
package com.davidflanagan.examples.basics;
/**
 * This class shows a recursive method to compute factorials.  This method
 * calls itself repeatedly based on the formula: n! = n * (n-1)!
 **/
public class Factorial2 {
    public static long factorial(long x) {
	if (x < 0) throw new IllegalArgumentException("x must be >= 0");
        if (x <= 1) return 1;              // Stop recursing here
        else return x * factorial(x-1);    // Recurse by calling ourselves
    }
}