Java中两个大数之间的相关运算及BigInteger代码示例

import java.util.Scanner;
/*
 进行大数相减，只能对两个正数进行相减
*/
public class BigNumber
{
	public static void main(String[] args)
	  {
		Scanner scan=new Scanner(System.in);
		String a,b;
		while (scan.hasNext())
		    {
			BigNumber big=new BigNumber();
			a=scan.nextLine();
			b=scan.nextLine();
			System.out.println(big.bigNumberSub(a,b));
		}
	}
	public String bigNumberSub(String x,String y)
	  {
		//String result=null;
		char[] a=x.toCharArray();
		char[] b=y.toCharArray();
		int lenA=a.length;
		int lenB=b.length;
		int len=lenA>lenB?lenA:lenB;
		int[] result=new int[len];
		//字符串反转
		char[] A=new char[lenA];
		char[] B=new char[lenB];
		for (int i=0;i<lenA;i++)
		    {
			A[i]=a[lenA-i-1];
		}
		for (int j=0;j<lenB;j++)
		    {
			B[j]=b[lenB-j-1];
		}
		//判断最终结果的正负
		char sign='+';
		if (lenA<lenB)
		    {
			sign='-';
		} else if(lenA>lenB)
		    {
			sign='+';
		} else
		    {
			for (int i=lenA-1;i>=0;i--)
			      {
				if (A[i]<B[i])
				        {
					sign='-';
					break;
				} else if(A[i]>B[i])
				        {
					sign='+';
					break;
				}
			}
		}
		//      
		int aint,bint;
		for (int i=0;i<len;i++)
		    {
			aint=i<lenA?A[i]-'0':0;
			bint=i<lenB?B[i]-'0':0;
			if (sign=='+')
			      {
				result[i]=aint-bint;
			} else 
			      {
				result[i]=bint-aint;
			}
		}
		//借位处理
		for (int j=0;j<len;j++)
		    {
			if (result[j]<0)
			      {
				result[j+1]=result[j+1]-1;
				result[j]=result[j]+10;
			}
		}
		//将结果对应为0的位置取消掉
		StringBuilder sb=new StringBuilder();
		Boolean flag=true;
		//防止结果集中的地位出现0
		if (sign=='-')
		    {
			sb.append(sign);
		}
		for (int i=len-1;i>=0;i--)
		    {
			if (result[i]==0&&flag)
			      {
			} else
			      {
				sb.append(result[i]);
				flag=false;
			}
		}
		return sb.toString();
		//return result;
	}
}

import java.util.Scanner;
import java.math.BigInteger;
/*
 进行大数相加，
*/
public class BigNumber
{
	public static void main(String[] args)
	  {
		Scanner scan=new Scanner(System.in);
		while (scan.hasNext())
		    {
			BigInteger b1=new BigInteger(scan.nextLine());
			BigInteger b2=new BigInteger(scan.nextLine());
			System.out.println(b1.add(b2));
			//System.out.println(000);
		}
	}
}

/**
 * 大数运算
 * BigInteger
 * 求91的5次方
 * 求它除以100的余数
 * 大数运算Biginteger类的方法调用
 */
package com.test1;
import java.math.*;
import java.math.BigInteger;
public class test100 {
  /**
   * @param args
   */
  static BigInteger k=BigInteger.valueOf(1);
  static BigInteger j=BigInteger.valueOf(91);
  static BigInteger n;
  BigDecimal l=new BigDecimal("100");
  static BigInteger m=new BigInteger("100");
  public static void main(String[] args) {
    // TODO Auto-generatedmethod stub
//   k=BigInteger.valueOf(1);
//   k=new BigInteger("1");
    for(int i=1;i<=5;i++){
      k=k.multiply(j);
      System.out.println(k.toString());
//     n=k.remainder(m);
      n=k.remainder(m);
      System.out.println(n.toString());
    }
  }
}