java 数字序列_关于java中任意长度数字序列的数值处理过程（面试常问问题）

如果基本的整数和浮点数精度不能够满足需求，那么可以使用java.math包中的两个很有用的类：BigInteger和BigDecimal。

BigInteger类实现了任意精度的整数运算

BigDecimal实现了任何精度的浮点数运算

使用静态的valueof()方法可以将普通数值转换为大数值(BigInteger a = BigInteger.valueOf(100);)

遗憾的是，不能使用人们熟悉的算术运算符(如：+和*)使用大数值，而需要使用大数值类中的add和multiply方法

import java.math.*;

import java.util.*;

/**

* This program uses big numbers to compute the odds of winning the grand prize in a lottery.

* @version 1.20 2004-02-10

* @author Cay Horstmann

*/

public class BigIntegerTest

{

public static void main(String[] args)

{

Scanner in = new Scanner(System.in);

System.out.print("How many numbers do you need to draw? ");

int k = in.nextInt();

System.out.print("What is the highest number you can draw? ");

int n = in.nextInt();

/*

* compute binomial coefficient n*(n-1)*(n-2)*...*(n-k+1)/(1*2*3*...*k)

*/

BigInteger lotteryOdds = BigInteger.valueOf(1);

for (int i = 1; i <= k; i++)

lotteryOdds = lotteryOdds.multiply(BigInteger.valueOf(n - i + 1)).divide(

BigInteger.valueOf(i));

System.out.println("Your odds are 1 in " + lotteryOdds + ". Good luck!");

}

}