Class DoubleFormatUtil

java.lang.Object
org.apache.xmlgraphics.util.DoubleFormatUtil

public final class DoubleFormatUtil extends Object
This class implements fast, thread-safe format of a double value with a given number of decimal digits.

The contract for the format methods is this one: if the source is greater than or equal to 1 (in absolute value), use the decimals parameter to define the number of decimal digits; else, use the precision parameter to define the number of decimal digits.

A few examples (consider decimals being 4 and precision being 8):

  • 0.0 should be rendered as "0"
  • 0.1 should be rendered as "0.1"
  • 1234.1 should be rendered as "1234.1"
  • 1234.1234567 should be rendered as "1234.1235" (note the trailing 5! Rounding!)
  • 1234.00001 should be rendered as "1234"
  • 0.00001 should be rendered as "0.00001" (here you see the effect of the "precision" parameter)
  • 0.00000001 should be rendered as "0.00000001"
  • 0.000000001 should be rendered as "0"
Originally authored by Julien Aymé.
  • Field Summary

    Fields
    Modifier and Type
    Field
    Description
    private static final double[]
     
    private static final long[]
    Most used power of ten (to avoid the cost of Math.pow(10, n)
  • Constructor Summary

    Constructors
    Modifier
    Constructor
    Description
    private
     
  • Method Summary

    Modifier and Type
    Method
    Description
    private static void
    format(StringBuffer target, int scale, long intP, long decP)
    Helper method to do the custom rounding used within formatDoublePrecise
    static void
    formatDouble(double source, int decimals, int precision, StringBuffer target)
    Rounds the given source value at the given precision and writes the rounded value into the given target
    static void
    formatDoubleFast(double source, int decimals, int precision, StringBuffer target)
    Rounds the given source value at the given precision and writes the rounded value into the given target
    static void
    formatDoublePrecise(double source, int decimals, int precision, StringBuffer target)
    Rounds the given source value at the given precision and writes the rounded value into the given target
    static int
    getExponant(double value)
    Returns the exponent of the given value
    private static boolean
    isRoundedToZero(double source, int decimals, int precision)
    Returns true if the given source value will be rounded to zero
    static long
    tenPow(int n)
    Returns ten to the power of n
    private static double
    tenPowDouble(int n)
     
    private static boolean
    tooCloseToRound(double source, int scale)
    Returns true if the given source is considered to be too close of a rounding value for the given scale.
    private static boolean
    tooManyDigitsUsed(double source, int scale)
    Returns true if the rounding is considered to use too many digits of the double for a fast rounding

    Methods inherited from class java.lang.Object

    clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait
  • Field Details

    • POWERS_OF_TEN_LONG

      private static final long[] POWERS_OF_TEN_LONG
      Most used power of ten (to avoid the cost of Math.pow(10, n)
    • POWERS_OF_TEN_DOUBLE

      private static final double[] POWERS_OF_TEN_DOUBLE
  • Constructor Details

    • DoubleFormatUtil

      private DoubleFormatUtil()
  • Method Details

    • formatDouble

      public static void formatDouble(double source, int decimals, int precision, StringBuffer target)
      Rounds the given source value at the given precision and writes the rounded value into the given target
      Parameters:
      source - the source value to round
      decimals - the decimals to round at (use if abs(source) ≥ 1.0)
      precision - the precision to round at (use if abs(source) < 1.0)
      target - the buffer to write to
    • formatDoublePrecise

      public static void formatDoublePrecise(double source, int decimals, int precision, StringBuffer target)
      Rounds the given source value at the given precision and writes the rounded value into the given target

      This method internally uses the String representation of the source value, in order to avoid any double precision computation error.

      Parameters:
      source - the source value to round
      decimals - the decimals to round at (use if abs(source) ≥ 1.0)
      precision - the precision to round at (use if abs(source) < 1.0)
      target - the buffer to write to
    • isRoundedToZero

      private static boolean isRoundedToZero(double source, int decimals, int precision)
      Returns true if the given source value will be rounded to zero
      Parameters:
      source - the source value to round
      decimals - the decimals to round at (use if abs(source) ≥ 1.0)
      precision - the precision to round at (use if abs(source) < 1.0)
      Returns:
      true if the source value will be rounded to zero
    • tenPow

      public static long tenPow(int n)
      Returns ten to the power of n
      Parameters:
      n - the nth power of ten to get
      Returns:
      ten to the power of n
    • tenPowDouble

      private static double tenPowDouble(int n)
    • format

      private static void format(StringBuffer target, int scale, long intP, long decP)
      Helper method to do the custom rounding used within formatDoublePrecise
      Parameters:
      target - the buffer to write to
      scale - the expected rounding scale
      intP - the source integer part
      decP - the source decimal part, truncated to scale + 1 digit
    • formatDoubleFast

      public static void formatDoubleFast(double source, int decimals, int precision, StringBuffer target)
      Rounds the given source value at the given precision and writes the rounded value into the given target

      This method internally uses double precision computation and rounding, so the result may not be accurate (see formatDouble method for conditions).

      Parameters:
      source - the source value to round
      decimals - the decimals to round at (use if abs(source) ≥ 1.0)
      precision - the precision to round at (use if abs(source) < 1.0)
      target - the buffer to write to
    • getExponant

      public static int getExponant(double value)
      Returns the exponent of the given value
      Parameters:
      value - the value to get the exponent from
      Returns:
      the value's exponent
    • tooManyDigitsUsed

      private static boolean tooManyDigitsUsed(double source, int scale)
      Returns true if the rounding is considered to use too many digits of the double for a fast rounding
      Parameters:
      source - the source to round
      scale - the scale to round at
      Returns:
      true if the rounding will potentially use too many digits
    • tooCloseToRound

      private static boolean tooCloseToRound(double source, int scale)
      Returns true if the given source is considered to be too close of a rounding value for the given scale.
      Parameters:
      source - the source to round
      scale - the scale to round at
      Returns:
      true if the source will be potentially rounded at the scale