All Implemented Interfaces and Traits:

java.util.Comparator

static class VersionsComparator.AlphaDecimalComparator

The returned comparator compares two character sequences as though each of them would be first transformed into a tuple of the form:

(A0, N0, A1, N1, ..., An-1, Nn-1, An, Nn)

A0 and An are (possibly empty) sub-sequences consisting of non-decimal-digit characters,

A1 ... An-1 are non-empty sub-sequences consisting of non-decimal-digit characters,

N0 ... Nn-1 are non-empty sub-sequences consisting of decimal-digit characters, and

Nn is a (possibly empty) sub-sequence consisting of decimal-digit characters.

All sub-sequences concatenated together in order as they appear in the tuple yield the original character sequence. After transformation, the tuples are compared by their elements (from left to right) so that corresponding Ax elements are compared using the provided comparator alphaComparator and Nx elements are compared as non negative decimal integers. The first pair of compared elements that is different with respect to the used comparator (either alphaComparator, or special decimal comparator) if any, provides the result produced by this comparator. The arguments are treated equal, if and only if all the subsequences, both decimal and non-decimal, compare equal.

For example, the following array was sorted using such comparator:

{ "1ab", "5ab", "10ab",
   "a1b", "a5b", "a10b",
   "ab1", "ab5", "ab10" ;}

When comparing numerical parts, an empty character sequence is considered less than any non-empty sequence of decimal digits.

If the numeric values of two compared character sub-sequences are equal, but their string representations have different number of leading zeroes, the comparator treats the number with less leading zeros as smaller. For example, "abc 1" < "abc 01" < "abc 001".

apiNote:

For example, to sort a collection of String based on case-insensitive ordering, and treating numbers with more leading zeroes as greater, one could use

Comparator<String> cmp = Comparator.comparingAlphaDecimal(
             Comparator.comparing(CharSequence::toString,
                                  String::compareToIgnoreCase));

implSpec:

To test if the given code point represents a decimal digit, the comparator checks if java.lang.Character#getType(int) returns value java.lang.Character#DECIMAL_DIGIT_NUMBER. The comparator uses java.lang.Character#digit(int, int) with the second argument set to 10 to determine the numeric value of a digit represented by the given code point.

throws:

NullPointerException if the argument is null

Parameters:

alphaComparator - the comparator that compares sub-sequences consisting of non-decimal-digits

- the type of elements to be compared; normally java.lang.CharSequence

Returns:

a comparator that compares character sequences, following the rules described above