工具类收集--GreatNumber.java

GreatNumber.java实现了两个超大数值(整数或浮点数都可以)的相加，也可以进行精度控制。

package org.siyn.util;

/** *//**
 * “超大数”实用类
 * @author siyn
 * @date 2008-04-27
 *
 */
public class GreatNumber
{
    private GreatNumber(){}
    
    /** *//**
     * 超大数字相加
     * 
     * @param {String}greatNumber1 待加“超大数1”
     * @param {String}greatNumber2 待加“超大数2”
     * @param {int}precision 精度(如果为负数，不限精度)
     * 
     * @return String 两个“超大数”之和
     * @throws NumberFormatException 
     */
    public static String add(String greatNumber1,String greatNumber2,int precision) throws RuntimeException
    {
        StringBuffer result = new StringBuffer("");
        //小数部分Fractional part
        String greatNumber1_FraPart = "";
        String greatNumber2_FraPart = "";
        //整数部分Integral part
        String greatNumber1_IntPart = "";
        String greatNumber2_IntPart = "";
        //小数点位置
        int locationOfDot = 0;
        //整数的小数部分补充0
        String zero = "";
        
        for(int i=0;i<precision ;i++)
        {
            zero +="0";
        }
        
        
        //划分整数部分和小数部分
        if(greatNumber1.indexOf('.')==-1)
        {
            greatNumber1_FraPart = zero;
            greatNumber1_IntPart = greatNumber1;
        }
        else
        {
            locationOfDot = greatNumber1.indexOf('.');
            greatNumber1_FraPart = greatNumber1.substring(locationOfDot+1);
            greatNumber1_IntPart = greatNumber1.substring(0,locationOfDot);
        }
        //System.out.println("greatNumber1="+greatNumber1_IntPart+"."+greatNumber1_FraPart);
        
        if(greatNumber2.indexOf('.')==-1)
        {
            greatNumber2_FraPart = zero;
            greatNumber2_IntPart = greatNumber2;
        }
        else
        {
            locationOfDot = greatNumber2.indexOf('.');
            greatNumber2_FraPart = greatNumber2.substring(locationOfDot+1);
            greatNumber2_IntPart = greatNumber2.substring(0,locationOfDot);
        }
        //System.out.println("greatNumber2="+greatNumber2_IntPart+"."+greatNumber2_FraPart);
        
        //小数部分
        StringBuffer result_FraPart = new StringBuffer();
        int carry = 0;
        int g1_FraPart_len = greatNumber1_FraPart.length();
        int g2_FraPart_len = greatNumber2_FraPart.length();
        int len = g1_FraPart_len>g2_FraPart_len?g1_FraPart_len:g2_FraPart_len;
        
        //精度控制
        if(precision<0)precision = len;
        len = len<precision?precision:len;//取大
        //String up_FraPart = g1_FraPart_len>g2_FraPart_len?greatNumber1_FraPart:greatNumber2_FraPart;
        //if(precision<up_FraPart.length()) carry = up_FraPart.charAt(precision)-48>4?1:0;
        
        for(int i=len-1;i>=0;i--)
        {
            char c1 = g1_FraPart_len > i?greatNumber1_FraPart.charAt(i):'0';
            char c2 = g2_FraPart_len > i?greatNumber2_FraPart.charAt(i):'0';

            if(Character.isDigit(c1) && Character.isDigit(c2))
            {
                int c = ( (c1-48)+(c2-48)+carry )%10;
                //进位
                if(i==precision)
                {
                    carry = ( (c1-48)+(c2-48)+carry )/5;
                    carry = carry>0?1:0;
                }
                else
                {
                    carry = ( (c1-48)+(c2-48)+carry )/10;
                }
                
                //精度控制
                if(i<precision) result_FraPart.insert(0, c);
                
            }
            else
            {
                throw new NumberFormatException("输入参数存在非数字字符.");
            }
        }
        
        
        //整数部分
        StringBuffer result_IntPart = new StringBuffer("");
        int g1_IntPart_len = greatNumber1_IntPart.length();
        int g2_IntPart_len = greatNumber2_IntPart.length();
        len = g1_IntPart_len>g2_IntPart_len?g1_IntPart_len:g2_IntPart_len;

        for(int i=0;i<len;i++)
        {
            char c1 = g1_IntPart_len > i?greatNumber1_IntPart.charAt(g1_IntPart_len-1-i):'0';
            char c2 = g2_IntPart_len > i?greatNumber2_IntPart.charAt(g2_IntPart_len-1-i):'0';
            
            if(Character.isDigit(c1) && Character.isDigit(c2))
            {
                int c = ( (c1-48)+(c2-48)+carry )%10;
                carry = ( (c1-48)+(c2-48)+carry )/10;
                result_IntPart.insert(0, c);
            }
            else
            {
                throw new NumberFormatException("输入参数存在非数字字符.");
            }
        }
        if(carry!=0) result_IntPart.insert(0, carry);//最后一个进位
            
        result.append(result_IntPart);
        result.append(".");
        result.append(result_FraPart);
        
        return result.toString();
    }
    
    /** *//**
     * 超大数字相加(不限精度)
     * 
     * @param {String}greatNumber1 待加超大数1
     * @param {String}greatNumber2 待加超大数1
     * 
     * @return String 两个超大数之和
     * @throws NumberFormatException 
     */
    public static String add(String greatNumber1,String greatNumber2) throws RuntimeException
    {
        return GreatNumber.add(greatNumber1, greatNumber2, -1);
    }
    
    public static void main(String[] aa)
    {
        String greatNumber1 = "9999999999999999999999999999999999999983.123456789";
        String greatNumber2 = "17.2";
        String result = GreatNumber.add(greatNumber1, greatNumber2,-6);
        System.out.println("   " + greatNumber1);
        System.out.println(" + " + greatNumber2);
        System.out.println("----------------------------------------------------------");
        System.out.println(" = " + result);
    }
}

弄好了才发现sun提供类BigDecimal＆BigInteger实现这个功能，哎~~~~