Java大数处理

Ⅰ基本函数：

1.valueOf(parament); 将参数转换为制定的类型

比如 int a=3;

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BigInteger b=BigInteger.valueOf(a);

则b=3;

String s=”12345”;

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BigInteger c=BigInteger.valueOf(s);

则c=12345；

2.add(); 大整数相加

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BigInteger a=new BigInteger(“23”);

BigInteger b=new BigInteger(“34”);

a. add(b);

3.subtract(); 相减

4.multiply(); 相乘

5.divide(); 相除取整

6.remainder(); 取余

7.pow(); a.pow(b)=a^b

8.gcd(); 最大公约数

9.abs(); 绝对值

10.negate(); 取反数

11.mod(); a.mod(b)=a%b=a.remainder(b);

12.max(); min();

13.punlic int comareTo();

14.boolean equals(); 是否相等

15.BigInteger构造函数：

一般用到以下两种：

BigInteger(String val);

将指定字符串转换为十进制表示形式；

BigInteger(String val,int radix);

将指定基数的 BigInteger 的字符串表示形式转换为 BigInteger

Ⅱ.基本常量：

A=BigInteger.ONE 1

B=BigInteger.TEN 10

C=BigInteger.ZERO 0

Ⅲ.基本操作

1. 读入：

用Scanner类定义对象进行控制台读入,Scanner类在java.util.*包中

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Scanner cin=new Scanner(System.in);// 读入

while(cin.hasNext()) //等同于!=EOF

{

int n;

BigInteger m;

n=cin.nextInt(); //读入一个int;

m=cin.BigInteger();//读入一个BigInteger;

System.out.print(m.toString());

}

Ⅳ.运用

四则预算：

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import java.util.Scanner;

import java.math.*;

import java.text.*;

public class Main

{

public static void main(String args[])

{

Scanner cin = new Scanner ( System.in );

BigInteger a,b;

int c;

char op;

String s;

while( cin.hasNext() )

{

a = cin.nextBigInteger();

s = cin.next();

op = s.charAt(0);

if( op == '+')

{

b = cin.nextBigInteger();

System.out.println(a.add(b));

}

else if( op == '-')

{

b = cin.nextBigInteger();

System.out.println(a.subtract(b));

}

else if( op == '*')

{

b = cin.nextBigInteger();

System.out.println(a.multiply(b));

}

else

{

BigDecimal a1,b1,eps;

String s1,s2,temp;

s1 = a.toString();

a1 = new BigDecimal(s1);

b = cin.nextBigInteger();

s2 = b.toString();

b1 = new BigDecimal(s2);

c = cin.nextInt();

eps = a1.divide(b1,c,4);

//System.out.println(a + " " + b + " " + c);

//System.out.println(a1.doubleValue() + " " + b1.doubleValue() + " " + c);

System.out.print( a.divide(b) + " " + a.mod(b) + " ");

if( c != 0)

{

temp = "0.";

for(int i = 0; i < c; i ++) temp += "0";

DecimalFormat gd = new DecimalFormat(temp);

System.out.println(gd.format(eps));

}

else System.out.println(eps);

}

}

}

}