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@adamcbuckley
Created January 16, 2020 17:37
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A java.util.Comparator for version (or chapter) numbers, which have an arbitrary number of decimal points.
package com.hebdensoft;
import java.util.Comparator;
/**
* <p>A java.util.Comparator for version (or chapter) numbers, which have an arbitrary number of decimal points.</p>
* <p>The code was taken from https://bugs.openjdk.java.net/browse/JDK-8134512 and http://cr.openjdk.java.net/~igerasim/8134512/04/webrev/index.html</p>
* <p>How to use:</p>
* <p><code>myListOfVersionNumbers.sort(VersionNumberComparator.getInstance());</code></p>
* <p>The code snippet would convert this list:</p>
* <ul>
* <li>1.1</li>
* <li>1.2</li>
* <li>1</li>
* <li>1.3</li>
* <li>1.1.1</li>
* <li>5.6</li>
* <li>1.1.10</li>
* <li>4</li>
* <li>1.1.9</li>
* <li>1.2.1.10</li>
* <li>2.1.1.4.5</li>
* <li>1.2.1.9</li>
* <li>1.2.1</li>
* <li>2.2.2</li>
* <li>1.2.1.11</li>
* </ul>
* <p>Into this list</p>
* <ul>
* <li>1</li>
* <li>1.1</li>
* <li>1.1.1</li>
* <li>1.1.9</li>
* <li>1.1.10</li>
* <li>1.2</li>
* <li>1.2.1</li>
* <li>1.2.1.9</li>
* <li>1.2.1.10</li>
* <li>1.2.1.11</li>
* <li>1.3</li>
* <li>2.1.1.4.5</li>
* <li>2.2.2</li>
* <li>4</li>
* <li>5.6</li>
* </ul>
*/
public class VersionNumberComparator {
public static VersionNumberComparator.AlphaDecimalComparator<String> getInstance() {
return new VersionNumberComparator.AlphaDecimalComparator<>(Comparator.comparing(CharSequence::toString, Comparator.naturalOrder()), false);
}
/**
* Compares char sequences, taking into account their numeric part if one exists.
*/
public static class AlphaDecimalComparator<T extends CharSequence> implements Comparator<T> {
private final Comparator<? super CharSequence> alphaComparator;
private final Comparator<CharSequence> decimalComparator;
AlphaDecimalComparator(Comparator<? super CharSequence> alphaComparator, boolean leadingZeroesFirst) {
this(alphaComparator, DecimalComparator.getInstance(leadingZeroesFirst));
}
private AlphaDecimalComparator(Comparator<? super CharSequence> alphaComparator, Comparator<CharSequence> decimalComparator) {
this.alphaComparator = alphaComparator;
this.decimalComparator = decimalComparator;
}
@Override
public Comparator<T> reversed() {
return new AlphaDecimalComparator<>(alphaComparator.reversed(),
decimalComparator.reversed());
}
@Override
public int compare(T cs1, T cs2) {
Decomposer d1 = new Decomposer(cs1);
Decomposer d2 = new Decomposer(cs2);
for (; ; ) {
int cmp;
if ((cmp = alphaComparator.compare(d1.get(), d2.get())) != 0 ||
(cmp = decimalComparator.compare(d1.get(), d2.get())) != 0) {
return cmp;
}
if (d1.eos() && d2.eos()) return 0;
}
}
/**
* Given a CharSequence, splits it into a series of subsequences so that
* every character of the very first subsequence (possibly empty) is
* not a decimal digit; then every character of the second subsequence
* is a decimal digit, and so on.
*/
private static class Decomposer {
private final CharSequence sequence;
private boolean expectingDecimal = false;
private int index = 0;
Decomposer(CharSequence sequence) {
this.sequence = sequence;
}
CharSequence get() {
int start = index, end = start, len = sequence.length() - start;
while (len > 0) {
int cp = Character.codePointAt(sequence, end);
int ct = Character.getType(cp);
boolean isDecimal = (ct == Character.DECIMAL_DIGIT_NUMBER);
if (isDecimal ^ expectingDecimal) {
break;
}
int cpWidth = Character.charCount(cp);
end += cpWidth;
len -= cpWidth;
}
expectingDecimal = !expectingDecimal;
return sequence.subSequence(start, index = end);
}
boolean eos() {
return index >= sequence.length();
}
}
}
/**
* The comparator for comparing character sequences that consist solely
* of decimal digits. The result of comparing is as if the values were
* compared numerically.
*/
public static class DecimalComparator implements Comparator<CharSequence> {
private static final Comparator<CharSequence>
DECIMAL_COMPARATOR_LEADING_ZEROES_FIRST =
new DecimalComparator(true) {
@Override
public Comparator<CharSequence> reversed() {
return DECIMAL_COMPARATOR_LEADING_ZEROES_FIRST_REVERSED;
}
};
private static final Comparator<CharSequence>
DECIMAL_COMPARATOR_LEADING_ZEROES_LAST =
new DecimalComparator(false) {
@Override
public Comparator<CharSequence> reversed() {
return DECIMAL_COMPARATOR_LEADING_ZEROES_LAST_REVERSED;
}
};
private static final Comparator<CharSequence>
DECIMAL_COMPARATOR_LEADING_ZEROES_FIRST_REVERSED =
new DecimalComparator(true) {
@Override
public Comparator<CharSequence> reversed() {
return DECIMAL_COMPARATOR_LEADING_ZEROES_FIRST;
}
@Override
public int compare(CharSequence cs1, CharSequence cs2) {
return super.compare(cs2, cs1);
}
};
private static final Comparator<CharSequence>
DECIMAL_COMPARATOR_LEADING_ZEROES_LAST_REVERSED =
new DecimalComparator(false) {
@Override
public Comparator<CharSequence> reversed() {
return DECIMAL_COMPARATOR_LEADING_ZEROES_LAST;
}
@Override
public int compare(CharSequence cs1, CharSequence cs2) {
return super.compare(cs2, cs1);
}
};
private final boolean leadingZeroesFirst;
public DecimalComparator(boolean leadingZeroesFirst) {
this.leadingZeroesFirst = leadingZeroesFirst;
}
static Comparator<CharSequence> getInstance(boolean leadingZeroesFirst) {
return leadingZeroesFirst ? DECIMAL_COMPARATOR_LEADING_ZEROES_FIRST
: DECIMAL_COMPARATOR_LEADING_ZEROES_LAST;
}
private boolean canSkipLeadingZeroes(CharSequence s, int len) {
for (int i = 0; i < len; ) {
int cp = Character.codePointAt(s, i);
if (Character.digit(cp, 10) != 0)
return false;
i += Character.charCount(cp);
}
return true;
}
@Override
public int compare(CharSequence cs1, CharSequence cs2) {
int len1 = Character.codePointCount(cs1, 0, cs1.length());
int len2 = Character.codePointCount(cs2, 0, cs2.length());
int dlen = len1 - len2;
if (len1 == 0 || len2 == 0) {
return dlen;
} else if (dlen > 0) {
if (!canSkipLeadingZeroes(cs1, dlen))
return 1;
int off = Character.offsetByCodePoints(cs1, 0, dlen);
cs1 = cs1.subSequence(off, cs1.length());
} else if (dlen < 0) {
if (!canSkipLeadingZeroes(cs2, -dlen))
return -1;
int off = Character.offsetByCodePoints(cs2, 0, -dlen);
cs2 = cs2.subSequence(off, cs2.length());
}
int cmp = 0;
for (int i1 = 0, i2 = 0; i1 < cs1.length(); ) {
int cp1 = Character.codePointAt(cs1, i1);
int cp2 = Character.codePointAt(cs2, i2);
if (cp1 != cp2) {
if (cmp == 0) {
cmp = cp1 - cp2;
}
int cmpNum = Character.digit(cp1, 10) -
Character.digit(cp2, 10);
if (cmpNum != 0) {
return cmpNum;
}
}
i1 += Character.charCount(cp1);
i2 += Character.charCount(cp2);
}
return dlen == 0 ? cmp : (leadingZeroesFirst ^ (dlen < 0) ? -1 : 1);
}
}
}
@dankirkd
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This doesn't support the Semantic Versioning rules of precedence. Using the VersionNumberComparator referred to in this answer when we want [1.0.0-alpha, 1.0.0-alpha.1, 1.0.0-alpha.beta, 1.0.0-beta, 1.0.0-beta.2, 1.0.0-beta.11, 1.0.0-rc.1, 1, 1.0, 1.0.0, 2.0.0, 2.2.0, 2.10.0] we instead get [1, 1.0, 1.0.0, 1.0.0-alpha, 1.0.0-alpha.1, 1.0.0-alpha.beta, 1.0.0-beta, 1.0.0-beta.2, 1.0.0-beta.11, 1.0.0-rc.1, 2.0.0, 2.2.0, 2.10.0]

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