package org.apache.lucene.util;
import java.util.Comparator;
import java.util.StringTokenizer;
/**
* Licensed to the Apache Software Foundation (ASF) under one or more
* contributor license agreements. See the NOTICE file distributed with
* this work for additional information regarding copyright ownership.
* The ASF licenses this file to You 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.
*/
/**
* Methods for manipulating strings.
*
* @lucene.internal
*/
public abstract class StringHelper {
/**
* Expert:
* The StringInterner implementation used by Lucene.
* This shouldn't be changed to an incompatible implementation after other Lucene APIs have been used.
*/
public static StringInterner interner = new SimpleStringInterner(1024,8);
/** Return the same string object for all equal strings */
public static String intern(String s) {
return interner.intern(s);
}
/**
* Compares two byte[] arrays, element by element, and returns the
* number of elements common to both arrays.
*
* @param bytes1 The first byte[] to compare
* @param bytes2 The second byte[] to compare
* @return The number of common elements.
*/
public static final int bytesDifference(byte[] bytes1, int len1, byte[] bytes2, int len2) {
int len = len1 < len2 ? len1 : len2;
for (int i = 0; i < len; i++)
if (bytes1[i] != bytes2[i])
return i;
return len;
}
private StringHelper() {
}
/**
* @return a Comparator over versioned strings such as X.YY.Z
* @lucene.internal
*/
public static Comparator<String> getVersionComparator() {
return versionComparator;
}
private static Comparator<String> versionComparator = new Comparator<String>() {
public int compare(String a, String b) {
StringTokenizer aTokens = new StringTokenizer(a, ".");
StringTokenizer bTokens = new StringTokenizer(b, ".");
while (aTokens.hasMoreTokens()) {
int aToken = Integer.parseInt(aTokens.nextToken());
if (bTokens.hasMoreTokens()) {
int bToken = Integer.parseInt(bTokens.nextToken());
if (aToken != bToken) {
return aToken < bToken ? -1 : 1;
}
} else {
// a has some extra trailing tokens. if these are all zeroes, thats ok.
if (aToken != 0) {
return 1;
}
}
}
// b has some extra trailing tokens. if these are all zeroes, thats ok.
while (bTokens.hasMoreTokens()) {
if (Integer.parseInt(bTokens.nextToken()) != 0)
return -1;
}
return 0;
}
};
}