How to round 0 745 to 0 75 using BigDecimal ROUND HALF UP

Question

I tried the following      double doubleVal   1 745     double doubleVal1   0 745     BigDecimal bdTest   new BigDecimal   doubleVal      BigDecimal bdTest1   new BigDecimal   doubleVal1       bdTest   bdTest setScale 2  BigDecimal ROUND HALF UP      bdTest1   bdTest1 setScale 2  BigDecimal ROUND HALF UP      System out println  bdTest   bdTest     1 75    System out println  bdTest1   bdTest1    0 74    problemmmm                  but got weird results  Why

User · Answer

double doubleVal   1 745  double doubleVal1   0 745  System out println new BigDecimal doubleVal    System out println new BigDecimal doubleVal1      outputs   1 74500000000000010658141036401502788066864013671875 0 74499999999999999555910790149937383830547332763671875   Which shows the real value of the two doubles and explains the result you get  As pointed out by others  don t use the double constructor  apart from the specific case where you want to see the actual value of a double    More about double precision    here there

User · Answer

This will maybe give you a hint on what went wrong   import java math BigDecimal   public class Main       public static void main String   args            BigDecimal bdTest   new BigDecimal 0 745           BigDecimal bdTest1   new BigDecimal  0 745            bdTest   bdTest setScale 2  BigDecimal ROUND HALF UP           bdTest1   bdTest1 setScale 2  BigDecimal ROUND HALF UP           System out println  bdTest     bdTest      prints  bdTest 0 74          System out println  bdTest1     bdTest1      prints  bdTest 0 75            The problem is  that your input  a double x 0 745   can not represent 0 745 exactly  It actually saves a value slightly lower  For BigDecimals  this is already below 0 745  so it rounds down     Try not to use the BigDecimal double float  constructors

User · Answer

Use BigDecimal valueOf double d  instead of new BigDecimal double d   The last one has precision errors by float and double

User · Answer

various option are available such as   Double d  123 12  BigDecimal b   new BigDecimal d  MathContext DECIMAL64      b   123 1200000 b   b setScale 2  BigDecimal ROUND HALF UP       b   123 12  BigDecimal b1  new BigDecimal collectionFileData getAmount    MathContext DECIMAL64  setScale 2  BigDecimal ROUND HALF UP      b1  123 12   d    double  Math round d   100    100  BigDecimal b2   new BigDecimal d toString         b2  123 12

User · Answer

For your interest  to do the same with double  double doubleVal   1 745  double doubleVal2   0 745  doubleVal   Math round doubleVal   100   0 005    100 0  doubleVal2   Math round doubleVal2   100   0 005    100 0  System out println  bdTest      doubleVal     1 75 System out println  bdTest1      doubleVal2    0 75   or just  double doubleVal   1 745  double doubleVal2   0 745  System out printf  bdTest    2f n    doubleVal   System out printf  bdTest1    2f n    doubleVal2     both print  bdTest  1 75 bdTest1  0 75   I prefer to keep code as simple as possible      As  mshutov notes  you need to add a little more to ensure that a half value always rounds up  This is because numbers like 265 335 are a little less than they appear

User · Answer

Never construct BigDecimals from floats or doubles  Construct them from ints or strings  floats and doubles loose precision   This code works as expected  I just changed the type from double to String    public static void main String   args      String doubleVal    1 745     String doubleVal1    0 745     BigDecimal bdTest   new BigDecimal   doubleVal     BigDecimal bdTest1   new BigDecimal   doubleVal1      bdTest   bdTest setScale 2  BigDecimal ROUND HALF UP     bdTest1   bdTest1 setScale 2  BigDecimal ROUND HALF UP     System out println  bdTest   bdTest     1 75   System out println  bdTest1   bdTest1    0 75  no problem

[java] How to round 0.745 to 0.75 using BigDecimal.ROUND_HALF_UP?

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