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/*
* GNU LESSER GENERAL PUBLIC LICENSE
* Version 3, 29 June 2007
*
* Copyright (C) 2007 Free Software Foundation, Inc.
* This comparator is based on the AlphanumComparator found at http://www.DaveKoelle.com and has been rewritten and modified by Daniel Sawano.
*
* This source can be found at https://github.com/sawano/alphanumeric-comparator
*
* Note: this algorithm does not take into account numeric notation such as decimals, negative numbers, scientific notation etc.
*
* @author Daniel Sawano
*/
public class AlphanumericComparator implements Comparator {
private final Collator collator;
/**
* Creates a comparator that will use lexicographical sorting of the non-numerical parts of the compared strings.
*/
public AlphanumericComparator() {
collator = null;
}
/**
* Creates a comparator that will use locale-sensitive sorting of the non-numerical parts of the compared strings.
*
* @param locale
* the locale to use
*/
public AlphanumericComparator(final Locale locale) {
this(Collator.getInstance(requireNonNull(locale)));
}
/**
* Creates a comparator that will use the given collator to sort the non-numerical parts of the compared strings.
*
* @param collator
* the collator to use
*/
public AlphanumericComparator(final Collator collator) {
this.collator = requireNonNull(collator);
}
@Override
public int compare(final String s1, final String s2) {
final CharBuffer b1 = wrap(s1);
final CharBuffer b2 = wrap(s2);
while (b1.remaining() > 0 && b2.remaining() > 0) {
final int result = compare(nextToken(b1), nextToken(b2));
if (result != 0) {
return result;
}
}
return s1.length() - s2.length();
}
private int compare(final CharBuffer s1, final CharBuffer s2) {
if (isNumeric(s1) && isNumeric(s2)) {
final int numericalResult = compareNumerically(s1, s2);
if (numericalResult != 0) {
return numericalResult;
}
}
return compareStrings(s1.toString(), s2.toString());
}
private int compareStrings(final String s1, final String s2) {
if (collator == null) {
return s1.compareTo(s2);
}
return collator.compare(s1, s2);
}
private CharBuffer nextToken(final CharBuffer s) {
final int endOfToken = positionOfNextDigitBoundary(s);
final CharBuffer token = s.subSequence(0, endOfToken - s.position());
s.position(endOfToken);
return token;
}
private int positionOfNextDigitBoundary(final CharBuffer s) {
int endPos = s.position();
final boolean firstWasDigit = isDigit(s.get(s.position()));
while (endPos < s.limit() && firstWasDigit == isDigit(s.get(endPos))) {
++endPos;
}
return endPos;
}
private boolean isNumeric(final CharBuffer string) {
return isDigit(string.get(string.position()));
}
private boolean isDigit(final char c) {
if (collator == null) {
final int cInt = (int) c;
return cInt >= 48 && cInt <= 57;
}
return Character.isDigit(c);
}
private int compareNumerically(final CharBuffer s1, CharBuffer s2) {
trimLeadingZeros(s1);
trimLeadingZeros(s2);
if (s1.remaining() != s2.remaining()) {
return s1.remaining() - s2.remaining();
}
while (s1.hasRemaining()) {
final int result = Character.compare(s1.get(), s2.get());
if (result != 0) {
return result;
}
}
return 0;
}
private void trimLeadingZeros(final CharBuffer numericalString) {
while (numericalString.remaining() > 0 && numericalString.get(numericalString.position()) == '0') {
numericalString.position(numericalString.position() + 1);
}
}
}