[java04]java大數類

[java04]java大數類

基本的整數和浮點數精度不滿足要求的時候可以使用java提供的BigInteger類和BigDecimal類。

java.math.BigInteger

java.math.BigInteger提供的方法：

BigInteger add(BigInteger other) BigInteger subtract(BigInteger other) BigInteger multiply(BigInteger other) BigInteger divide(BigIntegr other) int compareto(BigInteger other) BigInteger mod(BigInteger other)

static BigInteger valueOf(long x)

valueOf方法可以將普通的數值轉換為大數值：

BigInteger a＝BigInteger.valueOf(100);

輸出febonacci數列

輸出febonacci數列前100項，大約在93項時會超出long的範圍：

public static void  fibonacci(){        long[] a=new long[100];        for(int i=0;i<100;i++){            if(i==0){                a[0]=0;                System.out.print(a[i]+"\t");                continue;            }else if(i==1){                a[1]=1;                System.out.print(a[i]+"\t");                continue;            }            a[i]=a[i-1]+a[i-2];            System.out.print(a[i]+"\t");            if((i+1)%5==0){System.out.println("");}        }    }

改進：<喎?http://www.bkjia.com/kf/ware/vc/" target="_blank" class="keylink">vcD4NCjxwcmUgY2xhc3M9"brush:java;">public static void fibonacci() { BigInteger[] a = new BigInteger[200]; for (int i = 0; i < 200; i++) { if (i == 0) { a[0] = BigInteger.valueOf(0); System.out.print(a[i] + "\t"); continue; } else if (i == 1) { a[1] = BigInteger.valueOf(1); System.out.print(a[i] + "\t"); continue; } a[i] = a[i - 1].add(a[i - 2]); System.out.println("第" + i + "項:\t" + a[i] + "\t"); } }