Java使用BigDecimal解決浮點型運算丟失精度的問題

•     @Test
      public void test1(){
          System.out.print(0.05+0.01);
      }

  

•     @Test
      public void test2(){
          BigDecimal b1 = new BigDecimal(0.01);
          BigDecimal b2 = new BigDecimal(0.05);
          System.out.print(b1.add(b2));
      }

  

•     @Test
      public void test3(){
          BigDecimal b1 = new BigDecimal("0.01");
          BigDecimal b2 = new BigDecimal("0.05");
          System.out.print(b1.add(b2));
      }

  

• BigDecimal的加減乘除的工具類

  package com.mmall.util;
  
  import java.math.BigDecimal;
  
  public class BigDecimalUtil {
  
      private BigDecimalUtil(){
  
      }
  
      public static BigDecimal add(double v1,double v2){
          BigDecimal b1 = new BigDecimal(Double.toString(v1));
          BigDecimal b2 = new BigDecimal(Double.toString(v2));
          return b1.add(b2);
      }
  
      public static BigDecimal sub(double v1,double v2){
          BigDecimal b1 = new BigDecimal(Double.toString(v1));
          BigDecimal b2 = new BigDecimal(Double.toString(v2));
          return b1.subtract(b2);
      }
  
      public static BigDecimal mul(double v1,double v2){
          BigDecimal b1 = new BigDecimal(Double.toString(v1));
          BigDecimal b2 = new BigDecimal(Double.toString(v2));
          return b1.multiply(b2);
      }
  
      public static BigDecimal div(double v1,double v2){
          BigDecimal b1 = new BigDecimal(Double.toString(v1));
          BigDecimal b2 = new BigDecimal(Double.toString(v2));
          return b1.divide(b2,2,BigDecimal.ROUND_HALF_UP);//四舍五入,保留兩位小數
      }
  }