利用BigInteger计算Fibonacci数列,及解决大数阶乘

/**
 * 
 */
/*2010-9-29*/
/**
 * @author Administrator
 *
 */
import java.math.*;
public class hw12_20 {


	public static void main(String[] args) {
		// TODO Auto-generated method stub
		// 定义一个BigInteger类型变量
		BigInteger a = new BigInteger("8878465456454564564");
		BigInteger b = new BigInteger("5454465654564564");
		BigInteger c = a.add(b);
		
		System.out.println("a+b="+ a.add(b));
		System.out.println("a-b="+ a.subtract(b));
		System.out.println("a*b="+ a.max(b));
		System.out.println("a/b="+ a.divide(b));
		System.out.println("a^3="+ a.pow(3));
		System.out.println("gcd(a,b)="+ a.gcd(b));
		// 计算Fibonacci数列
		System.out.print(fibonac(20));
	}
	
	// 定义计算计算Fibonacci数列
	static BigInteger fibonac(int n)
	{

		if( n == 1)
			return BigInteger.valueOf(1);  // 返回1
		if( n == 2)
			return BigInteger.valueOf(2);  // 返回2
		else
			return fibonac(n-1).add(fibonac(n-2));
	}
}