Set specific precision of a BigDecimal

Question

I have an XSD that requires me to use a BigDecimal for a lat lon   I currently have the lat lon as doubles  and convert them to BigDecimal  but I am only required to use about 12 places of precision   I have not been able to figure out how to set that   Can anyone help me with this

User · Answer

Try this code          Integer perc   5      BigDecimal spread   BigDecimal ZERO       BigDecimal perc   spread setScale perc BigDecimal ROUND HALF UP       System out println perc     Result  0 00000

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The title of the question asks about precision  BigDecimal distinguishes between scale and precision  Scale is the number of decimal places  You can think of precision as the number of significant figures  also known as significant digits   Some examples in Clojure       scale     0 00123M    5   precision 0 00123M    3    In Clojure  The M designates a BigDecimal literal  You can translate the Clojure to Java if you like  but I find it to be more compact than Java    You can easily increase the scale     setScale 0 00123M 7    0 0012300M   But you can t decrease the scale in the exact same way     setScale 0 00123M 3    ArithmeticException Rounding necessary   You ll need to pass a rounding mode too     setScale 0 00123M 3 BigDecimal ROUND HALF EVEN      Note  BigDecimal would prefer that you use the MathContext rounding   constants  but I don t have them at my fingertips right now    So  it is easy to change the scale  But what about precision  This is not as easy as you might hope   It is easy to decrease the precision     round 3 14159M  java math MathContext  3     3 14M   But it is not obvious how to increase the precision     round 3 14159M  java math MathContext  7     3 14159M  unexpected    For the skeptical  this is not just a matter of trailing zeros not being displayed     precision   round 3 14159M  java math MathContext  7      6     same as above  still unexpected    FWIW  Clojure is careful with trailing zeros and will show them   4 0000M   4 0000M   precision 4 0000M    5   Back on track    You can try using a BigDecimal constructor  but it does not set the precision any higher than the number of digits you specify    BigDecimal   3   java math MathContext  5     3M  BigDecimal   3 1   java math MathContext  5     3 1M   So  there is no quick way to change the precision  I ve spent time fighting this while writing up this question and with a project I m working on  I consider this  at best  A CRAZYTOWN API  and at worst a bug  People  Seriously   So  best I can tell  if you want to change precision  you ll need to do these steps    Lookup the current precision  Lookup the current scale  Calculate the scale change  Set the new scale   These steps  as Clojure code    def x 0 000691M    the input number  def p  1    desired precision  def s       scale x  p   -   precision x       desired new scale   setScale x s  BigDecimal ROUND HALF EVEN    0 0007M   I know  this is a lot of steps just to change the precision   Why doesn t BigDecimal already provide this  Did I overlook something

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BigDecimal decPrec    BigDecimal yo get  Avg     decPrec   decPrec setScale 5  RoundingMode CEILING    String value  String valueOf decPrec     This way you can set specific precision of a BigDecimal   The value of decPrec was 1 5726903423607562595809913132345426 which is rounded off to 1 57267

User · Answer

You can use setScale   e g   double d       BigDecimal db   new BigDecimal d  setScale 12  BigDecimal ROUND HALF UP

[java] Set specific precision of a BigDecimal

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