数学运算工具类

Java代码 

 import java.math.BigDecimal;

 public class NumberUtil {

     private static final int DEFAULT_DIV_SCALE = 10;

     /**
      * 相加
      * @param v1
      * @param v2
      * @return double
      */
     public static double add(double v1, double v2)

     {

         BigDecimal b1 = new BigDecimal(Double.toString(v1));

         BigDecimal b2 = new BigDecimal(Double.toString(v2));

         return b1.add(b2).doubleValue();

     }


     public static String add(String v1, String v2)

     {

         BigDecimal b1 = new BigDecimal(v1);

         BigDecimal b2 = new BigDecimal(v2);

         return b1.add(b2).toString();

     }

     /**
      * 相减
      * @param v1
      * @param v2
      * @return
      */
     public static double subtract(double v1, double v2)

     {

         BigDecimal b1 = new BigDecimal(Double.toString(v1));

         BigDecimal b2 = new BigDecimal(Double.toString(v2));

         return b1.subtract(b2).doubleValue();

     }

     public static String subtract(String v1, String v2)

     {

         BigDecimal b1 = new BigDecimal(v1);

         BigDecimal b2 = new BigDecimal(v2);

         return b1.subtract(b2).toString();

     }

     /**
      * 相乘
      * @param v1
      * @param v2
      * @return
      */
     public static double multiply(double v1, double v2)

     {

         BigDecimal b1 = new BigDecimal(Double.toString(v1));

         BigDecimal b2 = new BigDecimal(Double.toString(v2));

         return b1.multiply(b2).doubleValue();

     }

     public static String multiply(String v1, String v2)

     {

         BigDecimal b1 = new BigDecimal(v1);

         BigDecimal b2 = new BigDecimal(v2);

         return b1.multiply(b2).toString();

     }

     /**
      * 相除
      * @param v1
      * @param v2
      * @return double
      */
     public static double divide(double v1, double v2)

     {

         return divide(v1, v2, DEFAULT_DIV_SCALE);

     }

     public static double divide(double v1, double v2, int scale)

     {

         return divide(v1, v2, scale, BigDecimal.ROUND_HALF_EVEN);

     }

     public static double divide(double v1, double v2, int scale, int round_mode) {

         if (scale < 0)

         {

             throw new IllegalArgumentException(
                     "The scale must be a positive integer or zero");

         }

         BigDecimal b1 = new BigDecimal(Double.toString(v1));

         BigDecimal b2 = new BigDecimal(Double.toString(v2));

         return b1.divide(b2, scale, round_mode).doubleValue();

     }

     public static String divide(String v1, String v2)

     {

         return divide(v1, v2, DEFAULT_DIV_SCALE);

     }

     public static String divide(String v1, String v2, int scale)

     {

         return divide(v1, v2, DEFAULT_DIV_SCALE, BigDecimal.ROUND_HALF_EVEN);

     }

     public static String divide(String v1, String v2, int scale, int round_mode)

     {

         if (scale < 0)

         {

             throw new IllegalArgumentException(
                     "The scale must be a positive integer or zero");

         }

         BigDecimal b1 = new BigDecimal(v1);

         BigDecimal b2 = new BigDecimal(v2);

         return b1.divide(b2, scale, round_mode).toString();

     }

     public static double round(double v, int scale)

     {

         return round(v, scale, BigDecimal.ROUND_HALF_EVEN);

     }

     public static double round(double v, int scale, int round_mode)

     {

         if (scale < 0)

         {

             throw new IllegalArgumentException(
                     "The scale must be a positive integer or zero");

         }

         BigDecimal b = new BigDecimal(Double.toString(v));

         return b.setScale(scale, round_mode).doubleValue();

     }

     public static String round(String v, int scale)

     {

         return round(v, scale, BigDecimal.ROUND_HALF_EVEN);

     }

     public static String round(String v, int scale, int round_mode)

     {

         if (scale < 0)

         {

             throw new IllegalArgumentException(
                     "The scale must be a positive integer or zero");

         }

         BigDecimal b = new BigDecimal(v);

         return b.setScale(scale, round_mode).toString();
     }

     public static void main(String[] args) {
         System.out.println(2.21 - 2);
         System.out.println(7 * 0.8);

         System.out.println(subtract(312.21, 312));
         System.out.println(multiply(7, 0.8));
     }

 }