Package org.apache.poi.ss.util

Class NumberComparer

  • public final class NumberComparer
extends java.lang.Object
    Excel compares numbers using different rules to those of java, so Double.compare(double, double) won't do.

    • Constructor Summary

      Constructors 
      Constructor Description
      NumberComparer()  

    • Method Summary

      All Methods Static Methods Concrete Methods 
      Modifier and Type Method Description
      static int compare​(double a, double b)
      This class attempts to reproduce Excel's behaviour for comparing numbers.

      • Methods inherited from class java.lang.Object

        equals, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

    • Constructor Detail

      • NumberComparer

        public NumberComparer()

    • Method Detail

      • compare

        public static int compare​(double a,
                          double b)
        This class attempts to reproduce Excel's behaviour for comparing numbers. Results are mostly the same as those from Double.compare(double, double) but with some rounding. For numbers that are very close, this code converts to a format having 15 decimal digits of precision and a decimal exponent, before completing the comparison.

        In Excel formula evaluation, expressions like "(0.06-0.01)=0.05" evaluate to "TRUE" even though the equivalent java expression is false. In examples like this, Excel achieves the effect by having additional logic for comparison operations.

        Note - Excel also gives special treatment to expressions like "0.06-0.01-0.05" which evaluates to "0" (in java, rounding anomalies give a result of 6.9E-18). The special behaviour here is for different reasons to the example above: If the last operator in a cell formula is '+' or '-' and the result is less than 250 times smaller than first operand, the result is rounded to zero. Needless to say, the two rules are not consistent and it is relatively easy to find examples that satisfy
        "A=B" is "TRUE" but "A-B" is not "0"
        and
        "A=B" is "FALSE" but "A-B" is "0"

        This rule (for rounding the result of a final addition or subtraction), has not been implemented in POI (as of Jul-2009).

        Returns:
        negative, 0, or positive according to the standard Excel comparison of values a and b.