StringTokenIterator.java
/*
* Copyright (c) 2008, Harald Kuhr
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions are met:
*
* * Redistributions of source code must retain the above copyright notice, this
* list of conditions and the following disclaimer.
*
* * Redistributions in binary form must reproduce the above copyright notice,
* this list of conditions and the following disclaimer in the documentation
* and/or other materials provided with the distribution.
*
* * Neither the name of the copyright holder nor the names of its
* contributors may be used to endorse or promote products derived from
* this software without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
* AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
* DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE
* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
* SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
* CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
* OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
* OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
*/
package com.twelvemonkeys.util;
import java.util.NoSuchElementException;
/**
* StringTokenIterator, a drop-in replacement for {@code StringTokenizer}.
* StringTokenIterator has the following features:
* <ul>
* <li>Iterates over a strings, 20-50% faster than {@code StringTokenizer}
* (and magnitudes faster than {@code String.split(..)} or
* {@code Pattern.split(..)})</li>
* <li>Implements the {@code Iterator} interface</li>
* <li>Optionally returns delimiters</li>
* <li>Optionally returns empty elements</li>
* <li>Optionally iterates in reverse</li>
* <li>Resettable</li>
* </ul>
*
* @see java.util.StringTokenizer
* @author <a href="mailto:harald.kuhr@gmail.com">Harald Kuhr</a>
* @author last modified by $Author: haku $
* @version $Id: //depot/branches/personal/haraldk/twelvemonkeys/release-2/twelvemonkeys-core/src/main/java/com/twelvemonkeys/util/StringTokenIterator.java#1 $
*/
public class StringTokenIterator extends AbstractTokenIterator {
private final String string;
private final char[] delimiters;
private int position;
private final int maxPosition;
private String next;
private String nextDelimiter;
private final boolean includeDelimiters;
private final boolean includeEmpty;
private final boolean reverse;
public final static int FORWARD = 1;
public final static int REVERSE = -1;
/**
* Stores the value of the delimiter character with the highest value.
* It is used to optimize the detection of delimiter characters.
*/
private final char maxDelimiter;
/**
* Creates a StringTokenIterator
*
* @param pString the string to be parsed.
*/
public StringTokenIterator(String pString) {
this(pString, " \t\n\r\f".toCharArray(), FORWARD, false, false);
}
/**
* Creates a StringTokenIterator
*
* @param pString the string to be parsed.
* @param pDelimiters the delimiters.
*/
public StringTokenIterator(String pString, String pDelimiters) {
this(pString, toCharArray(pDelimiters), FORWARD, false, false);
}
/**
* Creates a StringTokenIterator
*
* @param pString the string to be parsed.
* @param pDelimiters the delimiters.
* @param pDirection iteration direction.
*/
public StringTokenIterator(String pString, String pDelimiters, int pDirection) {
this(pString, toCharArray(pDelimiters), pDirection, false, false);
}
/**
* Creates a StringTokenIterator
*
* @param pString the string to be parsed.
* @param pDelimiters the delimiters.
* @param pIncludeDelimiters flag indicating whether to return delimiters as tokens.
*/
public StringTokenIterator(String pString, String pDelimiters, boolean pIncludeDelimiters) {
this(pString, toCharArray(pDelimiters), FORWARD, pIncludeDelimiters, false);
}
/**
* Creates a StringTokenIterator
*
* @param pString the string to be parsed.
* @param pDelimiters the delimiters.
* @param pDirection iteration direction.
* @param pIncludeDelimiters flag indicating whether to return delimiters as tokens.
* @param pIncludeEmpty flag indicating whether to return empty tokens
*
*/
public StringTokenIterator(String pString, String pDelimiters, int pDirection,
boolean pIncludeDelimiters, boolean pIncludeEmpty) {
this(pString, toCharArray(pDelimiters), pDirection, pIncludeDelimiters, pIncludeEmpty);
}
/**
* Implementation.
*
* @param pString the string to be parsed.
* @param pDelimiters the delimiters.
* @param pDirection iteration direction.
* @param pIncludeDelimiters flag indicating whether to return delimiters as tokens.
* @param pIncludeEmpty flag indicating whether to return empty tokens
*/
private StringTokenIterator(String pString, char[] pDelimiters,
int pDirection, boolean pIncludeDelimiters, boolean pIncludeEmpty) {
if (pString == null) {
throw new IllegalArgumentException("string == null");
}
string = pString;
maxPosition = pString.length();
delimiters = pDelimiters;
includeDelimiters = pIncludeDelimiters;
reverse = (pDirection == REVERSE);
includeEmpty = pIncludeEmpty;
maxDelimiter = initMaxDelimiter(pDelimiters);
reset();
}
private static char[] toCharArray(String pDelimiters) {
if (pDelimiters == null) {
throw new IllegalArgumentException("delimiters == null");
}
return pDelimiters.toCharArray();
}
/**
* Returns the highest char in the delimiter set.
* @param pDelimiters the delimiter set
* @return the highest char
*/
private static char initMaxDelimiter(char[] pDelimiters) {
if (pDelimiters == null) {
return 0;
}
char max = 0;
for (char c : pDelimiters) {
if (max < c) {
max = c;
}
}
return max;
}
/**
* Resets this iterator.
*
*/
public void reset() {
position = 0;
next = null;
nextDelimiter = null;
}
/**
* Returns {@code true} if the iteration has more elements. (In other
* words, returns {@code true} if {@code next} would return an element
* rather than throwing an exception.)
*
* @return {@code true} if the iterator has more elements.
*/
public boolean hasNext() {
return (next != null || fetchNext() != null);
}
private String fetchNext() {
// If next is delimiter, return fast
if (nextDelimiter != null) {
next = nextDelimiter;
nextDelimiter = null;
return next;
}
// If no more chars, return null
if (position >= maxPosition) {
return null;
}
return reverse ? fetchReverse() : fetchForward();
}
private String fetchReverse() {
// Get previous position
int prevPos = scanForPrev();
// Store next string
next = string.substring(prevPos + 1, maxPosition - position);
if (includeDelimiters && prevPos >= 0 && prevPos < maxPosition) {
nextDelimiter = string.substring(prevPos, prevPos + 1);
}
position = maxPosition - prevPos;
// Skip empty
if (next.length() == 0 && !includeEmpty) {
return fetchNext();
}
return next;
}
private String fetchForward() {
// Get next position
int nextPos = scanForNext();
// Store next string
next = string.substring(position, nextPos);
if (includeDelimiters && nextPos >= 0 && nextPos < maxPosition) {
nextDelimiter = string.substring(nextPos, nextPos + 1);
}
position = ++nextPos;
// Skip empty
if (next.length() == 0 && !includeEmpty) {
return fetchNext();
}
return next;
}
private int scanForNext() {
int position = this.position;
while (position < maxPosition) {
// Find next match, using all delimiters
char c = string.charAt(position);
if (c <= maxDelimiter) {
// Find first delimiter match
for (char delimiter : delimiters) {
if (c == delimiter) {
return position;// Return if match
}
}
}
// Next...
position++;
}
// Return last position, if no match
return position;
}
private int scanForPrev() {
int position = (maxPosition - 1) - this.position;
while (position >= 0) {
// Find next match, using all delimiters
char c = string.charAt(position);
if (c <= maxDelimiter) {
// Find first delimiter match
for (char delimiter : delimiters) {
if (c == delimiter) {
return position;// Return if match
}
}
}
// Next...
position--;
}
// Return first position, if no match
return position;
}
/**
* Returns the next element in the iteration.
*
* @return the next element in the iteration.
* @exception java.util.NoSuchElementException iteration has no more elements.
*/
public String next() {
if (!hasNext()) {
throw new NoSuchElementException();
}
String next = this.next;
this.next = fetchNext();
return next;
}
}