Round a double to 2 decimal places

Question

If the value is 200 3456  it should be formatted to 200 34  If it is 200  then it should be 200 00

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value    int  value   100   0 5    100 0

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function Double round2 Double val        return new BigDecimal val toString    setScale 2 RoundingMode HALF UP  doubleValue        Note the toString        This is because BigDecimal converts the exact binary form of the double     These are the various suggested methods and their fail cases      Always Good  new BigDecimal val toString    setScale 2 RoundingMode HALF UP  doubleValue     Double val   260 775d    EXPECTED 260 78 260 77 - WRONG - new BigDecimal val  setScale 2 RoundingMode HALF UP  doubleValue    Double val   260 775d    EXPECTED 260 78 260 77 - TRY AGAIN - Math round val   100 d    100 0d    Double val   256 025d    EXPECTED 256 03d 256 02 - OOPS - new DecimalFormat  0 00   format val      By default use half even  works if you change mode to half up   Double val   256 025d    EXPECTED 256 03d 256 02 - FAIL -  int  val   100   0 5    100 0

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double d   28786 079999999998  String str   String format   1 2f   d   d   Double valueOf str

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Rounding a double is usually not what one wants  Instead  use String format   to represent it in the desired format

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If you really want the same double  but rounded in the way you want you can use BigDecimal  for example  new BigDecimal myValue  setScale 2  RoundingMode HALF UP  doubleValue

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If you just want to print a double with two digits after the decimal point  use something like this   double value   200 3456  System out printf  Value    2f   value     If you want to have the result in a String instead of being printed to the console  use String format   with the same arguments   String result   String format    2f   value     Or use class DecimalFormat   DecimalFormat df   new DecimalFormat      0 00    System out println  Value      df format value

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The easiest way  would be to do a trick like this   double val         val   val 100  val   Math round val   val   val  100    if val starts at 200 3456 then it goes to 20034 56 then it gets rounded to 20035 then we divide it to get 200 34   if you wanted to always round down we could always truncate by casting to an int   double val         val   val 100  val    double   int  val   val   val  100    This technique will work for most cases because for very large doubles  positive or negative  it may overflow  but if you know that your values will be in an appropriate range then this should work for you

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double value  200 3456  DecimalFormat df   new DecimalFormat  0 00          System out println df format value

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I think this is easier   double time   200 3456  DecimalFormat df   new DecimalFormat                time   Double valueOf df format time     System out println time      200 35   Note that this will actually do the rounding for you  not just formatting

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For two rounding digits  Very simple and you are basically updating the variable instead of just display purposes which DecimalFormat does   x   Math floor x   100    100

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Please use Apache commons math   Precision round 10 4567  2

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In your question  it seems that you want to avoid rounding the numbers as well  I think  format   will round the numbers using half-up  afaik  so if you want to round  200 3456 should be 200 35 for a precision of 2  but in your case  if you just want the first 2 and then discard the rest   You could multiply it by 100 and then cast to an int  or taking the floor of the number   before dividing by 100 again     200 3456   100   20034 56     int  20034 56   20034    20034 100 0   200 34    You might have issues with really really big numbers close to the boundary though  In which case converting to a string and substring ing it would work just as easily

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Here s an utility that rounds  instead of truncating  a double to specified number of decimal places   For example   round 200 3456  2      returns 200 35   Original version  watch out with this  public static double round double value  int places        if  places  lt  0  throw new IllegalArgumentException         long factor    long  Math pow 10  places       value   value   factor      long tmp   Math round value       return  double  tmp   factor      This breaks down badly in corner cases with either a very high number of decimal places  e g  round 1000 0d  17   or large integer part  e g  round 90080070060 1d  9    Thanks to Sloin for pointing this out   I ve been using the above to round  not-too-big  doubles to 2 or 3 decimal places happily for years  for example to clean up time in seconds for logging purposes  27 987654321987 -  27 99   But I guess it s best to avoid it  since more reliable ways are readily available  with cleaner code too    So  use this instead   Adapted from this answer by Louis Wasserman and this one by Sean Owen    public static double round double value  int places        if  places  lt  0  throw new IllegalArgumentException         BigDecimal bd   BigDecimal valueOf value       bd   bd setScale places  RoundingMode HALF UP       return bd doubleValue        Note that HALF UP is the rounding mode  commonly taught at school   Peruse the RoundingMode documentation  if you suspect you need something else such as Bankers    Rounding   Of course  if you prefer  you can inline the above into a one-liner  new BigDecimal value  setScale places  RoundingMode HALF UP  doubleValue    And in every case  Always remember that floating point representations using float and double are inexact   For example  consider these expressions    999199 1231231235    999199 1231231236    true 1 03 - 0 41    0 6200000000000001   For exactness  you want to use BigDecimal  And while at it  use the constructor that takes a String  never the one taking double  For instance  try executing this   System out println new BigDecimal 1 03  subtract new BigDecimal 0 41     System out println new BigDecimal  1 03   subtract new BigDecimal  0 41        Some excellent further reading on the topic    Item 48   Avoid float and double if exact answers are required  in Effective Java  2nd ed  by Joshua Bloch What Every Programmer Should Know About Floating-Point Arithmetic     If you wanted String formatting instead of  or in addition to  strictly rounding numbers  see the other answers     Specifically  note that round 200  0  returns 200 0  If you want to output  200 00   you should first round and then format the result for output  which is perfectly explained in Jesper s answer

[java] Round a double to 2 decimal places

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