/**
* Copyright (C) 2011 Brian Ferris <bdferris@onebusaway.org>
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package org.onebusaway.utility.text;
import java.text.Collator;
/**
* Utility class for natural string order operations (a1 < a2 < a10). Written by
* Stephen Friedrich
* (http://weblogs.java.net/blog/skelvin/archive/2006/01/natural_string.html).
* No license specified? Code found at
* http://svn.atlassian.com/fisheye/browse/public
* /contrib/confluence/linking-plugin
* /trunk/src/java/com/eekboom/utils/Strings.java?r=1322&%40annotateMode=none
*
* TODO: Determine license situation
*/
public class NaturalStringOrder {
/**
* <p>
* A string comparator that does case sensitive comparisons and handles
* embedded numbers correctly.
* </p>
* <p>
* <b>Do not use</b> if your app might ever run on any locale that uses more
* than 7-bit ascii characters.
* </p>
* / private static final Comparator<String> NATURAL_COMPARATOR_ASCII = new
* Comparator<String>() { public int compare(String o1, String o2) { return
* compareNaturalAscii(o1, o2); } };
*
* /**
* <p>
* A string comparator that does case insensitive comparisons and handles
* embedded numbers correctly.
* </p>
* <p>
* <b>Do not use</b> if your app might ever run on any locale that uses more
* than 7-bit ascii characters.
* </p>
* / private static final Comparator<String>
* IGNORE_CASE_NATURAL_COMPARATOR_ASCII = new Comparator<String>() { public
* int compare(String o1, String o2) { return
* compareNaturalIgnoreCaseAscii(o1, o2); } };
*
* /** This is a utility class (static methods only), don't instantiate.
*/
private NaturalStringOrder() {
}
/**
* Returns a comparator that compares contained numbers based on their numeric
* values and compares other parts using the current locale's order rules.
* <p>
* For example in German locale this will be a comparator that handles umlauts
* correctly and ignores upper/lower case differences.
* </p>
*
* @return <p>
* A string comparator that uses the current locale's order rules and
* handles embedded numbers correctly.
* </p>
* @see #getNaturalComparator(java.text.Collator) / public static
* Comparator<String> getNaturalComparator() { Collator collator =
* Collator.getInstance(); return getNaturalComparator(collator); }
*
* /** Returns a comparator that compares contained numbers based on
* their numeric values and compares other parts using the given
* collator.
*
* @param collator used for locale specific comparison of text (non-number)
* subwords - must not be null
* @return <p>
* A string comparator that uses the given Collator to compare
* subwords and handles embedded numbers correctly.
* </p>
* @see #getNaturalComparator() / public static Comparator<String>
* getNaturalComparator(final Collator collator) { if(collator == null) {
* // it's important to explicitly handle this here - else the bug will
* manifest anytime later in possibly // unrelated code that tries to use
* the comparator throw new
* NullPointerException("collator must not be null"); } return new
* Comparator<String>() { public int compare(String o1, String o2) {
* return compareNatural(collator, o1, o2); } }; }
*
* /** Returns a comparator that compares contained numbers based on
* their numeric values and compares other parts based on each
* character's Unicode value.
*
* @return <p>
* a string comparator that does case sensitive comparisons on pure
* ascii strings and handles embedded numbers correctly.
* </p>
* <b>Do not use</b> if your app might ever run on any locale that
* uses more than 7-bit ascii characters.
* @see #getNaturalComparator()
* @see #getNaturalComparator(java.text.Collator) / public static
* Comparator<String> getNaturalComparatorAscii() { return
* NATURAL_COMPARATOR_ASCII; }
*
* /** Returns a comparator that compares contained numbers based on
* their numeric values and compares other parts based on each
* character's Unicode value while ignore upper/lower case differences.
* <b>Do not use</b> if your app might ever run on any locale that uses
* more than 7-bit ascii characters.
*
* @return <p>
* a string comparator that does case insensitive comparisons on pure
* ascii strings and handles embedded numbers correctly.
* </p>
* @see #getNaturalComparator()
* @see #getNaturalComparator(java.text.Collator) / public static
* Comparator<String> getNaturalComparatorIgnoreCaseAscii() { return
* IGNORE_CASE_NATURAL_COMPARATOR_ASCII; }
*
* /**
* <p>
* Compares two strings using the current locale's rules and comparing
* contained numbers based on their numeric values.
* </p>
* <p>
* This is probably the best default comparison to use.
* </p>
* <p>
* If you know that the texts to be compared are in a certain language
* that differs from the default locale's langage, then get a collator
* for the desired locale (
* {@link java.text.Collator#getInstance(java.util.Locale)}) and pass it
* to {@link #compareNatural(java.text.Collator, String, String)}
* </p>
*
* @param s first string
* @param t second string
* @return zero iff <code>s</code> and <code>t</code> are equal, a value less
* than zero iff <code>s</code> lexicographically precedes
* <code>t</code> and a value larger than zero iff <code>s</code>
* lexicographically follows <code>t</code>
*/
public static int compareNatural(String s, String t) {
return compareNatural(s, t, false, Collator.getInstance());
}
/**
* <p>
* Compares two strings using the given collator and comparing contained
* numbers based on their numeric values.
* </p>
*
* @param s first string
* @param t second string
* @return zero iff <code>s</code> and <code>t</code> are equal, a value less
* than zero iff <code>s</code> lexicographically precedes
* <code>t</code> and a value larger than zero iff <code>s</code>
* lexicographically follows <code>t</code>
*/
public static int compareNatural(Collator collator, String s, String t) {
return compareNatural(s, t, true, collator);
}
/**
* <p>
* Compares two strings using each character's Unicode value for non-digit
* characters and the numeric values off any contained numbers.
* </p>
* <p>
* (This will probably make sense only for strings containing 7-bit ascii
* characters only.)
* </p>
*
* @return zero iff <code>s</code> and <code>t</code> are equal, a value less
* than zero iff <code>s</code> lexicographically precedes
* <code>t</code> and a value larger than zero iff <code>s</code>
* lexicographically follows <code>t</code>
*/
public static int compareNaturalAscii(String s, String t) {
return compareNatural(s, t, true, null);
}
/**
* <p>
* Compares two strings using each character's Unicode value - ignoring
* upper/lower case - for non-digit characters and the numeric values of any
* contained numbers.
* </p>
* <p>
* (This will probably make sense only for strings containing 7-bit ascii
* characters only.)
* </p>
*
* @return zero iff <code>s</code> and <code>t</code> are equal, a value less
* than zero iff <code>s</code> lexicographically precedes
* <code>t</code> and a value larger than zero iff <code>s</code>
* lexicographically follows <code>t</code>
*/
public static int compareNaturalIgnoreCaseAscii(String s, String t) {
return compareNatural(s, t, false, null);
}
/**
* @param s first string
* @param t second string
* @param caseSensitive treat characters differing in case only as equal -
* will be ignored if a collator is given
* @param collator used to compare subwords that aren't numbers - if null,
* characters will be compared individually based on their Unicode
* value
* @return zero iff <code>s</code> and <code>t</code> are equal, a value less
* than zero iff <code>s</code> lexicographically precedes
* <code>t</code> and a value larger than zero iff <code>s</code>
* lexicographically follows <code>t</code>
*/
private static int compareNatural(String s, String t, boolean caseSensitive,
Collator collator) {
int sIndex = 0;
int tIndex = 0;
int sLength = s.length();
int tLength = t.length();
while (true) {
// both character indices are after a subword (or at zero)
// Check if one string is at end
if (sIndex == sLength && tIndex == tLength) {
return 0;
}
if (sIndex == sLength) {
return -1;
}
if (tIndex == tLength) {
return 1;
}
// Compare sub word
char sChar = s.charAt(sIndex);
char tChar = t.charAt(tIndex);
boolean sCharIsDigit = Character.isDigit(sChar);
boolean tCharIsDigit = Character.isDigit(tChar);
if (sCharIsDigit && tCharIsDigit) {
// Compare numbers
// skip leading 0s
int sLeadingZeroCount = 0;
while (sChar == '0') {
++sLeadingZeroCount;
++sIndex;
if (sIndex == sLength) {
break;
}
sChar = s.charAt(sIndex);
}
int tLeadingZeroCount = 0;
while (tChar == '0') {
++tLeadingZeroCount;
++tIndex;
if (tIndex == tLength) {
break;
}
tChar = t.charAt(tIndex);
}
boolean sAllZero = sIndex == sLength || !Character.isDigit(sChar);
boolean tAllZero = tIndex == tLength || !Character.isDigit(tChar);
if (sAllZero && tAllZero) {
continue;
}
if (sAllZero && !tAllZero) {
return -1;
}
if (tAllZero) {
return 1;
}
int diff = 0;
do {
if (diff == 0) {
diff = sChar - tChar;
}
++sIndex;
++tIndex;
if (sIndex == sLength && tIndex == tLength) {
return diff != 0 ? diff : sLeadingZeroCount - tLeadingZeroCount;
}
if (sIndex == sLength) {
if (diff == 0) {
return -1;
}
return Character.isDigit(t.charAt(tIndex)) ? -1 : diff;
}
if (tIndex == tLength) {
if (diff == 0) {
return 1;
}
return Character.isDigit(s.charAt(sIndex)) ? 1 : diff;
}
sChar = s.charAt(sIndex);
tChar = t.charAt(tIndex);
sCharIsDigit = Character.isDigit(sChar);
tCharIsDigit = Character.isDigit(tChar);
if (!sCharIsDigit && !tCharIsDigit) {
// both number sub words have the same length
if (diff != 0) {
return diff;
}
break;
}
if (!sCharIsDigit) {
return -1;
}
if (!tCharIsDigit) {
return 1;
}
} while (true);
} else {
// Compare words
if (collator != null) {
// To use the collator the whole subwords have to be compared -
// character-by-character comparision
// is not possible. So find the two subwords first
int aw = sIndex;
int bw = tIndex;
do {
++sIndex;
} while (sIndex < sLength && !Character.isDigit(s.charAt(sIndex)));
do {
++tIndex;
} while (tIndex < tLength && !Character.isDigit(t.charAt(tIndex)));
String as = s.substring(aw, sIndex);
String bs = t.substring(bw, tIndex);
int subwordResult = collator.compare(as, bs);
if (subwordResult != 0) {
return subwordResult;
}
} else {
// No collator specified. All characters should be ascii only. Compare
// character-by-character.
do {
if (sChar != tChar) {
if (caseSensitive) {
return sChar - tChar;
}
sChar = Character.toUpperCase(sChar);
tChar = Character.toUpperCase(tChar);
if (sChar != tChar) {
sChar = Character.toLowerCase(sChar);
tChar = Character.toLowerCase(tChar);
if (sChar != tChar) {
return sChar - tChar;
}
}
}
++sIndex;
++tIndex;
if (sIndex == sLength && tIndex == tLength) {
return 0;
}
if (sIndex == sLength) {
return -1;
}
if (tIndex == tLength) {
return 1;
}
sChar = s.charAt(sIndex);
tChar = t.charAt(tIndex);
sCharIsDigit = Character.isDigit(sChar);
tCharIsDigit = Character.isDigit(tChar);
} while (!sCharIsDigit && !tCharIsDigit);
}
}
}
}
}