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.
  • Method Summary

    Modifier and Type
    Method
    Description
    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
    static long
    tenPow(int n)
    Returns ten to the power of n

    Methods inherited from class java.lang.Object

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