Double value to round up in Java

Question

I have a double value   1 068879335 i want to round it up with only two decimal values like 1 07   I tried like this  DecimalFormat df new DecimalFormat  0 00    String formate   df format value   double finalValue   Double parseDouble formate      this is giving me this following exception   java lang NumberFormatException  For input string   1 07       at sun misc FloatingDecimal readJavaFormatString FloatingDecimal java 1224       at java lang Double parseDouble Double java 510    can some one tell me what is wrong with my code    finaly i need the finalValue   1 07

User · Answer

Try this  org apache commons math3 util Precision round double x  int scale   See  http   commons apache org proper commons-math apidocs org apache commons math3 util Precision html  Apache Commons Mathematics Library homepage is  http   commons apache org proper commons-math index html  The internal implemetation of this method is   public static double round double x  int scale        return round x  scale  BigDecimal ROUND HALF UP      public static double round double x  int scale  int roundingMethod        try           return  new BigDecimal                 Double toString x                   setScale scale  roundingMethod                   doubleValue          catch  NumberFormatException ex            if  Double isInfinite x                 return x            else               return Double NaN

User · Answer

There is something fundamentally wrong with what you re trying to do  Binary floating-points values do not have decimal places  You cannot meaningfully round one to a given number of decimal places  because most  round  decimal values simply cannot be represented as a binary fraction  Which is why one should never use float or double to represent money   So if you want decimal places in your result  that result must either be a String  which you already got with the DecimalFormat   or a BigDecimal  which has a setScale   method that does exactly what you want   Otherwise  the result cannot be what you want it to be   Read The Floating-Point Guide for more information

User · Answer

double TotalPrice 90 98989898898     DecimalFormat format 2Places   new DecimalFormat  0 00         TotalPrice   Double valueOf format 2Places format TotalPrice

User · Answer

This is not possible in the requested way because there are numbers with two decimal places which can not be expressed exactly using IEEE floating point numbers  for example 1 10   0 1 can not be expressed as a Double or Float   The formatting should always happen as the last step before presenting the result to the user   I guess you are asking because you want to deal with monetary values  There is no way to do this reliably with floating-point numbers  you shoud consider switching to fixed-point arithmetics  This probably means doing all calculations in  cents  instead of  dollars

User · Answer

If you do not want to use DecimalFormat  e g  due to its efficiency  and you want a general solution  you could also try this method that uses scaled rounding   public static double roundToDigits double value  int digitCount        if  digitCount  lt  0          throw new IllegalArgumentException  Digit count must be positive for rounding          double factor   Math pow 10  digitCount       return  double  Math round value   factor     factor

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Live  Sergey s solution but with integer division   double value   23 8764367843  double rounded    double  Math round value   100    100  System out println value    rounded is    rounded     prints  23 8764367843 rounded is 23 88   EDIT  As Sergey points out  there should be no difference between multipling double int and double double and dividing double int and double double   I can t find an example where the result is different   However on x86 x64 and other systems there is a specific machine code instruction for mixed double int values which I believe the JVM uses   for  int j   0  j  lt  11  j          long start   System nanoTime        for  double i   1  i  lt  1e6  i    1 0000001            double rounded    double  Math round i   100    100            long time   System nanoTime   - start      System out printf  double int operations   d n   time     for  int j   0  j  lt  11  j          long start   System nanoTime        for  double i   1  i  lt  1e6  i    1 0000001            double rounded    double  Math round i   100 0    100 0            long time   System nanoTime   - start      System out printf  double double operations   d n   time       Prints  double int operations 613 552 212 double int operations 661 823 569 double int operations 659 398 960 double int operations 659 343 506 double int operations 653 851 816 double int operations 645 317 212 double int operations 647 765 219 double int operations 655 101 137 double int operations 657 407 715 double int operations 654 858 858 double int operations 648 702 279 double double operations 1 178 561 102 double double operations 1 187 694 386 double double operations 1 184 338 024 double double operations 1 178 556 353 double double operations 1 176 622 937 double double operations 1 169 324 313 double double operations 1 173 162 162 double double operations 1 169 027 348 double double operations 1 175 080 353 double double operations 1 182 830 988 double double operations 1 185 028 544

User · Answer

You could try defining a new DecimalFormat and using it as a Double result to a new double variable   Example given to make you understand what I just said   double decimalnumber   100 2397  DecimalFormat dnf   new DecimalFormat               0 00     double roundednumber   new Double dnf format decimalnumber   doubleValue

User · Answer

The problem is that you use a localizing formatter that generates locale-specific decimal point  which is     in your case  But Double parseDouble   expects non-localized double literal  You could solve your problem by using a locale-specific parsing method or by changing locale of your formatter to something that uses     as the decimal point  Or even better  avoid unnecessary formatting by using something like this   double rounded    double  Math round value   100 0    100 0

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You can use format like here     public static double getDoubleValue String value int digit       if value  null           value  0              double i 0       try            DecimalFormat digitformat   new DecimalFormat                   digitformat setMaximumFractionDigits digit           return Double valueOf digitformat format Double parseDouble value            catch  NumberFormatException numberFormatExp            return i

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Note the comma in your string   1 07   DecimalFormat uses a locale-specific separator string  while Double parseDouble   does not  As you happen to live in a country where the decimal separator is      you can t parse your number back   However  you can use the same DecimalFormat to parse it back   DecimalFormat df new DecimalFormat  0 00    String formate   df format value    double finalValue    Double df parse formate      But you really should do this instead   double finalValue   Math round  value   100 0     100 0    Note  As has been pointed out  you should only use floating point if you don t need a precise control over accuracy   Financial calculations being the main example of when not to use them

[java] Double value to round up in Java

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