/*
    * 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
    *
    *      https://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.apache.commons.text;
  
  import java.util.ArrayList;
  import java.util.Arrays;
  import java.util.Collections;
  import java.util.List;
  import java.util.ListIterator;
  import java.util.NoSuchElementException;
  
  import org.apache.commons.lang3.ArrayUtils;
  import org.apache.commons.lang3.StringUtils;
  import org.apache.commons.text.matcher.StringMatcher;
  import org.apache.commons.text.matcher.StringMatcherFactory;
  
  /**
   * Tokenizes a string based on delimiters (separators) and supporting quoting and ignored character concepts.
   * <p>
   * This class can split a String into many smaller strings. It aims to do a similar job to
   * {@link java.util.StringTokenizer StringTokenizer}, however it offers much more control and flexibility including
   * implementing the {@code ListIterator} interface. By default, it is set up like {@code StringTokenizer}.
   * <p>
   * The input String is split into a number of <em>tokens</em>. Each token is separated from the next String by a
   * <em>delimiter</em>. One or more delimiter characters must be specified.
   * <p>
   * Each token may be surrounded by quotes. The <em>quote</em> matcher specifies the quote character(s). A quote may be
   * escaped within a quoted section by duplicating itself.
   * <p>
   * Between each token and the delimiter are potentially characters that need trimming. The <em>trimmer</em> matcher
   * specifies these characters. One usage might be to trim whitespace characters.
   * <p>
   * At any point outside the quotes there might potentially be invalid characters. The <em>ignored</em> matcher specifies
   * these characters to be removed. One usage might be to remove new line characters.
   * <p>
   * Empty tokens may be removed or returned as null.
   *
   * <pre>
   * "a,b,c"         - Three tokens "a","b","c"   (comma delimiter)
   * " a, b , c "    - Three tokens "a","b","c"   (default CSV processing trims whitespace)
   * "a, ", b ,", c" - Three tokens "a, " , " b ", ", c" (quoted text untouched)
   * </pre>
   *
   * <table>
   * <caption>StringTokenizer properties and options</caption>
   * <tr>
   * <th>Property</th>
   * <th>Type</th>
   * <th>Default</th>
   * </tr>
   * <tr>
   * <td>delim</td>
   * <td>CharSetMatcher</td>
   * <td>{ \t\n\r\f}</td>
   * </tr>
   * <tr>
   * <td>quote</td>
   * <td>NoneMatcher</td>
   * <td>{}</td>
   * </tr>
   * <tr>
   * <td>ignore</td>
   * <td>NoneMatcher</td>
   * <td>{}</td>
   * </tr>
   * <tr>
   * <td>emptyTokenAsNull</td>
   * <td>boolean</td>
   * <td>false</td>
   * </tr>
   * <tr>
   * <td>ignoreEmptyTokens</td>
   * <td>boolean</td>
   * <td>true</td>
   * </tr>
   * </table>
   *
   * @since 1.3
   */
  public class StringTokenizer implements ListIterator<String>, Cloneable {
  
      /** Comma separated values tokenizer internal variable. */
      // @formatter:off
      private static final StringTokenizer CSV_TOKENIZER_PROTOTYPE = new StringTokenizer()
              .setDelimiterMatcher(StringMatcherFactory.INSTANCE.commaMatcher())
             .setQuoteMatcher(StringMatcherFactory.INSTANCE.doubleQuoteMatcher())
             .setIgnoredMatcher(StringMatcherFactory.INSTANCE.noneMatcher())
             .setTrimmerMatcher(StringMatcherFactory.INSTANCE.trimMatcher())
             .setEmptyTokenAsNull(false)
             .setIgnoreEmptyTokens(false);
     // @formatter:on
 
     /** Tab separated values tokenizer internal variable. */
     // @formatter:off
     private static final StringTokenizer TSV_TOKENIZER_PROTOTYPE = new StringTokenizer()
             .setDelimiterMatcher(StringMatcherFactory.INSTANCE.tabMatcher())
             .setQuoteMatcher(StringMatcherFactory.INSTANCE.doubleQuoteMatcher())
             .setIgnoredMatcher(StringMatcherFactory.INSTANCE.noneMatcher())
             .setTrimmerMatcher(StringMatcherFactory.INSTANCE.trimMatcher())
             .setEmptyTokenAsNull(false)
             .setIgnoreEmptyTokens(false);
     // @formatter:on
 
     /**
      * Returns a clone of {@code CSV_TOKENIZER_PROTOTYPE}.
      *
      * @return a clone of {@code CSV_TOKENIZER_PROTOTYPE}.
      */
     private static StringTokenizer getCSVClone() {
         return (StringTokenizer) CSV_TOKENIZER_PROTOTYPE.clone();
     }
 
     /**
      * Gets a new tokenizer instance which parses Comma Separated Value strings initializing it with the given input.
      * The default for CSV processing will be trim whitespace from both ends (which can be overridden with the
      * setTrimmer method).
      * <p>
      * You must call a "reset" method to set the string which you want to parse.
      * </p>
      *
      * @return a new tokenizer instance which parses Comma Separated Value strings.
      */
     public static StringTokenizer getCSVInstance() {
         return getCSVClone();
     }
 
     /**
      * Gets a new tokenizer instance which parses Comma Separated Value strings initializing it with the given input. The default for CSV processing will be
      * trim whitespace from both ends (which can be overridden with the setTrimmer method).
      *
      * @param input the text to parse.
      * @return a new tokenizer instance which parses Comma Separated Value strings.
      */
     public static StringTokenizer getCSVInstance(final char[] input) {
         return getCSVClone().reset(input);
     }
 
     /**
      * Gets a new tokenizer instance which parses Comma Separated Value strings initializing it with the given input. The default for CSV processing will be
      * trim whitespace from both ends (which can be overridden with the setTrimmer method).
      *
      * @param input the text to parse.
      * @return a new tokenizer instance which parses Comma Separated Value strings.
      */
     public static StringTokenizer getCSVInstance(final String input) {
         return getCSVClone().reset(input);
     }
 
     /**
      * Returns a clone of {@code TSV_TOKENIZER_PROTOTYPE}.
      *
      * @return a clone of {@code TSV_TOKENIZER_PROTOTYPE}.
      */
     private static StringTokenizer getTSVClone() {
         return (StringTokenizer) TSV_TOKENIZER_PROTOTYPE.clone();
     }
 
     /**
      * Gets a new tokenizer instance which parses Tab Separated Value strings. The default for CSV processing will be
      * trim whitespace from both ends (which can be overridden with the setTrimmer method).
      * <p>
      * You must call a "reset" method to set the string which you want to parse.
      * </p>
      *
      * @return a new tokenizer instance which parses Tab Separated Value strings.
      */
     public static StringTokenizer getTSVInstance() {
         return getTSVClone();
     }
 
     /**
      * Gets a new tokenizer instance which parses Tab Separated Value strings. The default for CSV processing will be trim whitespace from both ends (which can
      * be overridden with the setTrimmer method).
      *
      * @param input the string to parse.
      * @return a new tokenizer instance which parses Tab Separated Value strings.
      */
     public static StringTokenizer getTSVInstance(final char[] input) {
         return getTSVClone().reset(input);
     }
 
     /**
      * Gets a new tokenizer instance which parses Tab Separated Value strings. The default for CSV processing will be trim whitespace from both ends (which can
      * be overridden with the setTrimmer method).
      *
      * @param input the string to parse.
      * @return a new tokenizer instance which parses Tab Separated Value strings.
      */
     public static StringTokenizer getTSVInstance(final String input) {
         return getTSVClone().reset(input);
     }
 
     /** The text to work on. */
     private char[] chars;
 
     /** The parsed tokens. */
     private String[] tokens;
 
     /** The current iteration position. */
     private int tokenPos;
 
     /** The delimiter matcher. */
     private StringMatcher delimMatcher = StringMatcherFactory.INSTANCE.splitMatcher();
 
     /** The quote matcher. */
     private StringMatcher quoteMatcher = StringMatcherFactory.INSTANCE.noneMatcher();
 
     /** The ignored matcher. */
     private StringMatcher ignoredMatcher = StringMatcherFactory.INSTANCE.noneMatcher();
 
     /** The trimmer matcher. */
     private StringMatcher trimmerMatcher = StringMatcherFactory.INSTANCE.noneMatcher();
 
     /** Whether to return empty tokens as null. */
     private boolean emptyAsNull;
 
     /** Whether to ignore empty tokens. */
     private boolean ignoreEmptyTokens = true;
 
     /**
      * Constructs a tokenizer splitting on space, tab, newline and form feed as per StringTokenizer, but with no text to tokenize.
      * <p>
      * This constructor is normally used with {@link #reset(String)}.
      * </p>
      */
     public StringTokenizer() {
         this.chars = null;
     }
 
     /**
      * Constructs a tokenizer splitting on space, tab, newline and form feed as per StringTokenizer.
      *
      * @param input the string which is to be parsed, not cloned.
      */
     public StringTokenizer(final char[] input) {
         this.chars = input != null ? input.clone() : null;
     }
 
     /**
      * Constructs a tokenizer splitting on the specified character.
      *
      * @param input the string which is to be parsed, not cloned.
      * @param delim the field delimiter character.
      */
     public StringTokenizer(final char[] input, final char delim) {
         this(input);
         setDelimiterChar(delim);
     }
 
     /**
      * Constructs a tokenizer splitting on the specified delimiter character and handling quotes using the specified quote character.
      *
      * @param input the string which is to be parsed, not cloned.
      * @param delim the field delimiter character.
      * @param quote the field quoted string character.
      */
     public StringTokenizer(final char[] input, final char delim, final char quote) {
         this(input, delim);
         setQuoteChar(quote);
     }
 
     /**
      * Constructs a tokenizer splitting on the specified string.
      *
      * @param input the string which is to be parsed, not cloned.
      * @param delim the field delimiter string.
      */
     public StringTokenizer(final char[] input, final String delim) {
         this(input);
         setDelimiterString(delim);
     }
 
     /**
      * Constructs a tokenizer splitting using the specified delimiter matcher.
      *
      * @param input the string which is to be parsed, not cloned.
      * @param delim the field delimiter matcher.
      */
     public StringTokenizer(final char[] input, final StringMatcher delim) {
         this(input);
         setDelimiterMatcher(delim);
     }
 
     /**
      * Constructs a tokenizer splitting using the specified delimiter matcher and handling quotes using the specified quote matcher.
      *
      * @param input the string which is to be parsed, not cloned.
      * @param delim the field delimiter character.
      * @param quote the field quoted string character.
      */
     public StringTokenizer(final char[] input, final StringMatcher delim, final StringMatcher quote) {
         this(input, delim);
         setQuoteMatcher(quote);
     }
 
     /**
      * Constructs a tokenizer splitting on space, tab, newline and form feed as per StringTokenizer.
      *
      * @param input the string which is to be parsed.
      */
     public StringTokenizer(final String input) {
         this.chars = input != null ? input.toCharArray() : null;
     }
 
     /**
      * Constructs a tokenizer splitting on the specified delimiter character.
      *
      * @param input the string which is to be parsed.
      * @param delim the field delimiter character.
      */
     public StringTokenizer(final String input, final char delim) {
         this(input);
         setDelimiterChar(delim);
     }
 
     /**
      * Constructs a tokenizer splitting on the specified delimiter character and handling quotes using the specified quote character.
      *
      * @param input the string which is to be parsed.
      * @param delim the field delimiter character.
      * @param quote the field quoted string character.
      */
     public StringTokenizer(final String input, final char delim, final char quote) {
         this(input, delim);
         setQuoteChar(quote);
     }
 
     /**
      * Constructs a tokenizer splitting on the specified delimiter string.
      *
      * @param input the string which is to be parsed.
      * @param delim the field delimiter string.
      */
     public StringTokenizer(final String input, final String delim) {
         this(input);
         setDelimiterString(delim);
     }
 
     /**
      * Constructs a tokenizer splitting using the specified delimiter matcher.
      *
      * @param input the string which is to be parsed.
      * @param delim the field delimiter matcher.
      */
     public StringTokenizer(final String input, final StringMatcher delim) {
         this(input);
         setDelimiterMatcher(delim);
     }
 
     /**
      * Constructs a tokenizer splitting using the specified delimiter matcher and handling quotes using the specified quote matcher.
      *
      * @param input the string which is to be parsed.
      * @param delim the field delimiter matcher.
      * @param quote the field quoted string matcher.
      */
     public StringTokenizer(final String input, final StringMatcher delim, final StringMatcher quote) {
         this(input, delim);
         setQuoteMatcher(quote);
     }
 
     /**
      * Unsupported ListIterator operation.
      *
      * @param obj this parameter ignored.
      * @throws UnsupportedOperationException always.
      */
     @Override
     public void add(final String obj) {
         throw new UnsupportedOperationException("add() is unsupported");
     }
 
     /**
      * Adds a token to a list, paying attention to the parameters we've set.
      *
      * @param list the list to add to.
      * @param tok  the token to add.
      */
     private void addToken(final List<String> list, String tok) {
         if (tok == null || tok.isEmpty()) {
             if (isIgnoreEmptyTokens()) {
                 return;
             }
             if (isEmptyTokenAsNull()) {
                 tok = null;
             }
         }
         list.add(tok);
     }
 
     /**
      * Checks if tokenization has been done, and if not then do it.
      */
     private void checkTokenized() {
         if (tokens == null) {
             final List<String> split;
             if (chars == null) {
                 // still call tokenize as subclass may do some work.
                 split = tokenize(null, 0, 0);
             } else {
                 split = tokenize(chars, 0, chars.length);
             }
             tokens = split.toArray(ArrayUtils.EMPTY_STRING_ARRAY);
         }
     }
 
     /**
      * Creates a new instance of this Tokenizer. The new instance is reset so that it will be at the start of the token list. If a
      * {@link CloneNotSupportedException} is caught, return {@code null}.
      *
      * @return a new instance of this Tokenizer which has been reset.
      */
     @Override
     public Object clone() {
         try {
             return cloneReset();
         } catch (final CloneNotSupportedException ex) {
             return null;
         }
     }
 
     /**
      * Creates a new instance of this Tokenizer. The new instance is reset so that it will be at the start of the token list.
      *
      * @return a new instance of this Tokenizer which has been reset.
      * @throws CloneNotSupportedException if there is a problem cloning.
      */
     Object cloneReset() throws CloneNotSupportedException {
         // this method exists to enable 100% test coverage
         final StringTokenizer cloned = (StringTokenizer) super.clone();
         if (cloned.chars != null) {
             cloned.chars = cloned.chars.clone();
         }
         cloned.reset();
         return cloned;
     }
 
     /**
      * Gets the String content that the tokenizer is parsing.
      *
      * @return The string content being parsed.
      */
     public String getContent() {
         if (chars == null) {
             return null;
         }
         return new String(chars);
     }
 
     /**
      * Gets the field delimiter matcher.
      *
      * @return The delimiter matcher in use.
      */
     public StringMatcher getDelimiterMatcher() {
         return this.delimMatcher;
     }
 
     /**
      * Gets the ignored character matcher.
      * <p>
      * These characters are ignored when parsing the String, unless they are within a quoted region. The default value is not to ignore anything.
      * </p>
      *
      * @return The ignored matcher in use.
      */
     public StringMatcher getIgnoredMatcher() {
         return ignoredMatcher;
     }
 
     /**
      * Gets the quote matcher currently in use.
      * <p>
      * The quote character is used to wrap data between the tokens. This enables delimiters to be entered as data. The default value is '"' (double quote).
      * </p>
      *
      * @return The quote matcher in use.
      */
     public StringMatcher getQuoteMatcher() {
         return quoteMatcher;
     }
 
     /**
      * Gets a copy of the full token list as an independent modifiable array.
      *
      * @return The tokens as a String array.
      */
     public String[] getTokenArray() {
         checkTokenized();
         return tokens.clone();
     }
 
     /**
      * Gets a copy of the full token list as an independent modifiable list.
      *
      * @return The tokens as a String list.
      */
     public List<String> getTokenList() {
         checkTokenized();
         return new ArrayList<>(Arrays.asList(tokens));
     }
 
     /**
      * Gets the trimmer character matcher.
      * <p>
      * These characters are trimmed off on each side of the delimiter until the token or quote is found. The default value is not to trim anything.
      * </p>
      *
      * @return The trimmer matcher in use.
      */
     public StringMatcher getTrimmerMatcher() {
         return trimmerMatcher;
     }
 
     /**
      * Tests whether there are any more tokens.
      *
      * @return true if there are more tokens.
      */
     @Override
     public boolean hasNext() {
         checkTokenized();
         return tokenPos < tokens.length;
     }
 
     /**
      * Tests whether there are any previous tokens that can be iterated to.
      *
      * @return true if there are previous tokens.
      */
     @Override
     public boolean hasPrevious() {
         checkTokenized();
         return tokenPos > 0;
     }
 
     /**
      * Tests whether the tokenizer currently returns empty tokens as null. The default for this property is false.
      *
      * @return true if empty tokens are returned as null.
      */
     public boolean isEmptyTokenAsNull() {
         return this.emptyAsNull;
     }
 
     /**
      * Tests whether the tokenizer currently ignores empty tokens. The default for this property is true.
      *
      * @return true if empty tokens are not returned.
      */
     public boolean isIgnoreEmptyTokens() {
         return ignoreEmptyTokens;
     }
 
     /**
      * Tests if the characters at the index specified match the quote already matched in readNextToken().
      *
      * @param srcChars   the character array being tokenized.
      * @param pos        the position to check for a quote.
      * @param len        the length of the character array being tokenized.
      * @param quoteStart the start position of the matched quote, 0 if no quoting.
      * @param quoteLen   the length of the matched quote, 0 if no quoting.
      * @return true if a quote is matched.
      */
     private boolean isQuote(final char[] srcChars, final int pos, final int len, final int quoteStart, final int quoteLen) {
         for (int i = 0; i < quoteLen; i++) {
             if (pos + i >= len || srcChars[pos + i] != srcChars[quoteStart + i]) {
                 return false;
             }
         }
         return true;
     }
 
     /**
      * Gets the next token.
      *
      * @return The next String token.
      * @throws NoSuchElementException if there are no more elements.
      */
     @Override
     public String next() {
         if (hasNext()) {
             return tokens[tokenPos++];
         }
         throw new NoSuchElementException();
     }
 
     /**
      * Gets the index of the next token to return.
      *
      * @return The next token index.
      */
     @Override
     public int nextIndex() {
         return tokenPos;
     }
 
     /**
      * Gets the next token from the String. Equivalent to {@link #next()} except it returns null rather than throwing {@link NoSuchElementException} when no
      * tokens remain.
      *
      * @return The next sequential token, or null when no more tokens are found.
      */
     public String nextToken() {
         if (hasNext()) {
             return tokens[tokenPos++];
         }
         return null;
     }
 
     /**
      * Gets the token previous to the last returned token.
      *
      * @return The previous token.
      */
     @Override
     public String previous() {
         if (hasPrevious()) {
             return tokens[--tokenPos];
         }
         throw new NoSuchElementException();
     }
 
     /**
      * Gets the index of the previous token.
      *
      * @return The previous token index.
      */
     @Override
     public int previousIndex() {
         return tokenPos - 1;
     }
 
     /**
      * Gets the previous token from the String.
      *
      * @return The previous sequential token, or null when no more tokens are found.
      */
     public String previousToken() {
         if (hasPrevious()) {
             return tokens[--tokenPos];
         }
         return null;
     }
 
     /**
      * Reads character by character through the String to get the next token.
      *
      * @param srcChars  the character array being tokenized.
      * @param start     the first character of field.
      * @param len       the length of the character array being tokenized.
      * @param workArea  a temporary work area.
      * @param tokenList the list of parsed tokens.
      * @return The starting position of the next field (the character immediately after the delimiter), or -1 if end of string found.
      */
     private int readNextToken(final char[] srcChars, int start, final int len, final TextStringBuilder workArea,
             final List<String> tokenList) {
         // skip all leading whitespace, unless it is the
         // field delimiter or the quote character
         while (start < len) {
             final int removeLen = Math.max(getIgnoredMatcher().isMatch(srcChars, start, start, len),
                     getTrimmerMatcher().isMatch(srcChars, start, start, len));
             if (removeLen == 0 || getDelimiterMatcher().isMatch(srcChars, start, start, len) > 0
                     || getQuoteMatcher().isMatch(srcChars, start, start, len) > 0) {
                 break;
             }
             start += removeLen;
         }
 
         // handle reaching end
         if (start >= len) {
             addToken(tokenList, StringUtils.EMPTY);
             return -1;
         }
 
         // handle empty token
         final int delimLen = getDelimiterMatcher().isMatch(srcChars, start, start, len);
         if (delimLen > 0) {
             addToken(tokenList, StringUtils.EMPTY);
             return start + delimLen;
         }
 
         // handle found token
         final int quoteLen = getQuoteMatcher().isMatch(srcChars, start, start, len);
         if (quoteLen > 0) {
             return readWithQuotes(srcChars, start + quoteLen, len, workArea, tokenList, start, quoteLen);
         }
         return readWithQuotes(srcChars, start, len, workArea, tokenList, 0, 0);
     }
 
     /**
      * Reads a possibly quoted string token.
      *
      * @param srcChars   the character array being tokenized.
      * @param start      the first character of field.
      * @param len        the length of the character array being tokenized.
      * @param workArea   a temporary work area.
      * @param tokenList  the list of parsed tokens.
      * @param quoteStart the start position of the matched quote, 0 if no quoting.
      * @param quoteLen   the length of the matched quote, 0 if no quoting.
      * @return The starting position of the next field (the character immediately after the delimiter, or if end of string found, then the length of string.
      */
     private int readWithQuotes(final char[] srcChars, final int start, final int len, final TextStringBuilder workArea,
             final List<String> tokenList, final int quoteStart, final int quoteLen) {
         // Loop until we've found the end of the quoted
         // string or the end of the input
         workArea.clear();
         int pos = start;
         boolean quoting = quoteLen > 0;
         int trimStart = 0;
 
         while (pos < len) {
             // quoting mode can occur several times throughout a string
             // we must switch between quoting and non-quoting until we
             // encounter a non-quoted delimiter, or end of string
             if (quoting) {
                 // In quoting mode
 
                 // If we've found a quote character, see if it's
                 // followed by a second quote. If so, then we need
                 // to actually put the quote character into the token
                 // rather than end the token.
                 if (isQuote(srcChars, pos, len, quoteStart, quoteLen)) {
                     if (isQuote(srcChars, pos + quoteLen, len, quoteStart, quoteLen)) {
                         // matched pair of quotes, thus an escaped quote
                         workArea.append(srcChars, pos, quoteLen);
                         pos += quoteLen * 2;
                         trimStart = workArea.size();
                         continue;
                     }
 
                     // end of quoting
                     quoting = false;
                     pos += quoteLen;
                     continue;
                 }
 
             } else {
                 // Not in quoting mode
 
                 // check for delimiter, and thus end of token
                 final int delimLen = getDelimiterMatcher().isMatch(srcChars, pos, start, len);
                 if (delimLen > 0) {
                     // return condition when end of token found
                     addToken(tokenList, workArea.substring(0, trimStart));
                     return pos + delimLen;
                 }
 
                 // check for quote, and thus back into quoting mode
                 if (quoteLen > 0 && isQuote(srcChars, pos, len, quoteStart, quoteLen)) {
                     quoting = true;
                     pos += quoteLen;
                     continue;
                 }
 
                 // check for ignored (outside quotes), and ignore
                 final int ignoredLen = getIgnoredMatcher().isMatch(srcChars, pos, start, len);
                 if (ignoredLen > 0) {
                     pos += ignoredLen;
                     continue;
                 }
 
                 // check for trimmed character
                 // don't yet know if its at the end, so copy to workArea
                 // use trimStart to keep track of trim at the end
                 final int trimmedLen = getTrimmerMatcher().isMatch(srcChars, pos, start, len);
                 if (trimmedLen > 0) {
                     workArea.append(srcChars, pos, trimmedLen);
                     pos += trimmedLen;
                     continue;
                 }
             }
             // copy regular character from inside quotes
             workArea.append(srcChars[pos++]);
             trimStart = workArea.size();
         }
 
         // return condition when end of string found
         addToken(tokenList, workArea.substring(0, trimStart));
         return -1;
     }
 
     /**
      * Throws {@link UnsupportedOperationException} for this unsupported ListIterator operation.
      *
      * @throws UnsupportedOperationException Always thrown.
      */
     @Override
     public void remove() {
         throw new UnsupportedOperationException("remove() is unsupported");
     }
 
     /**
      * Resets this tokenizer, forgetting all parsing and iteration already completed.
      * <p>
      * This method allows the same tokenizer to be reused for the same String.
      * </p>
      *
      * @return {@code this} instance.
      */
     public StringTokenizer reset() {
         tokenPos = 0;
         tokens = null;
         return this;
     }
 
     /**
      * Resets this tokenizer, giving it a new input string to parse. In this manner you can re-use a tokenizer with the same settings on multiple input lines.
      *
      * @param input the new character array to tokenize, not cloned, null sets no text to parse.
      * @return {@code this} instance.
      */
     public StringTokenizer reset(final char[] input) {
         reset();
         this.chars = input != null ? input.clone() : null;
         return this;
     }
 
     /**
      * Resets this tokenizer, giving it a new input string to parse. In this manner you can re-use a tokenizer with the same settings on multiple input lines.
      *
      * @param input the new string to tokenize, null sets no text to parse.
      * @return {@code this} instance.
      */
     public StringTokenizer reset(final String input) {
         reset();
         this.chars = input != null ? input.toCharArray() : null;
         return this;
     }
 
     /**
      * Throws {@link UnsupportedOperationException} for this unsupported ListIterator operation.
      *
      * @param obj this parameter ignored.
      * @throws UnsupportedOperationException always.
      */
     @Override
     public void set(final String obj) {
         throw new UnsupportedOperationException("set() is unsupported");
     }
 
     /**
      * Sets the field delimiter character.
      *
      * @param delim the delimiter character to use.
      * @return {@code this} instance.
      */
     public StringTokenizer setDelimiterChar(final char delim) {
         return setDelimiterMatcher(StringMatcherFactory.INSTANCE.charMatcher(delim));
     }
 
     /**
      * Sets the field delimiter matcher.
      * <p>
      * The delimiter is used to separate one token from another.
      * </p>
      *
      * @param delim the delimiter matcher to use.
      * @return {@code this} instance.
      */
     public StringTokenizer setDelimiterMatcher(final StringMatcher delim) {
         this.delimMatcher = delim == null ? StringMatcherFactory.INSTANCE.noneMatcher() : delim;
         return this;
     }
 
     /**
      * Sets the field delimiter string.
      *
      * @param delim the delimiter string to use.
      * @return {@code this} instance.
      */
     public StringTokenizer setDelimiterString(final String delim) {
         return setDelimiterMatcher(StringMatcherFactory.INSTANCE.stringMatcher(delim));
     }
 
     /**
      * Sets whether the tokenizer should return empty tokens as null. The default for this property is false.
      *
      * @param emptyAsNull whether empty tokens are returned as null.
      * @return {@code this} instance.
      */
     public StringTokenizer setEmptyTokenAsNull(final boolean emptyAsNull) {
         this.emptyAsNull = emptyAsNull;
         return this;
     }
 
     /**
      * Sets the character to ignore.
      * <p>
      * This character is ignored when parsing the String, unless it is within a quoted region.
      * </p>
      *
      * @param ignored the ignored character to use.
      * @return {@code this} instance.
      */
     public StringTokenizer setIgnoredChar(final char ignored) {
         return setIgnoredMatcher(StringMatcherFactory.INSTANCE.charMatcher(ignored));
     }
 
     /**
      * Sets the matcher for characters to ignore.
      * <p>
      * These characters are ignored when parsing the String, unless they are within a quoted region.
      * </p>
      *
      * @param ignored the ignored matcher to use, null ignored.
      * @return {@code this} instance.
      */
     public StringTokenizer setIgnoredMatcher(final StringMatcher ignored) {
         if (ignored != null) {
             this.ignoredMatcher = ignored;
         }
         return this;
     }
 
     /**
      * Sets whether the tokenizer should ignore and not return empty tokens. The default for this property is true.
      *
      * @param ignoreEmptyTokens whether empty tokens are not returned.
      * @return {@code this} instance.
      */
     public StringTokenizer setIgnoreEmptyTokens(final boolean ignoreEmptyTokens) {
         this.ignoreEmptyTokens = ignoreEmptyTokens;
         return this;
     }
 
     /**
      * Sets the quote character to use.
      * <p>
      * The quote character is used to wrap data between the tokens. This enables delimiters to be entered as data.
      * </p>
      *
      * @param quote the quote character to use.
      * @return {@code this} instance.
      */
     public StringTokenizer setQuoteChar(final char quote) {
         return setQuoteMatcher(StringMatcherFactory.INSTANCE.charMatcher(quote));
     }
 
     /**
      * Sets the quote matcher to use.
      * <p>
      * The quote character is used to wrap data between the tokens. This enables delimiters to be entered as data.
      * </p>
      *
      * @param quote the quote matcher to use, null ignored.
      * @return {@code this} instance.
      */
     public StringTokenizer setQuoteMatcher(final StringMatcher quote) {
         if (quote != null) {
             this.quoteMatcher = quote;
         }
         return this;
     }
 
     /**
      * Sets the matcher for characters to trim.
      * <p>
      * These characters are trimmed off on each side of the delimiter until the token or quote is found.
      *
      * @param trimmer the trimmer matcher to use, null ignored.
      * @return {@code this} instance.
      */
     public StringTokenizer setTrimmerMatcher(final StringMatcher trimmer) {
         if (trimmer != null) {
             this.trimmerMatcher = trimmer;
         }
         return this;
     }
 
     /**
      * Gets the number of tokens found in the String.
      *
      * @return The number of matched tokens.
      */
     public int size() {
         checkTokenized();
         return tokens.length;
     }
 
     /**
      * Internal method to performs the tokenization.
      * <p>
      * Most users of this class do not need to call this method. This method will be called automatically by other (public) methods when required.
      * </p>
      * <p>
      * This method exists to allow subclasses to add code before or after the tokenization. For example, a subclass could alter the character array, offset or
      * count to be parsed, or call the tokenizer multiple times on multiple strings. It is also be possible to filter the results.
      * </p>
      * <p>
      * {@code StrTokenizer} will always pass a zero offset and a count equal to the length of the array to this method, however a subclass may pass other
      * values, or even an entirely different array.
      * </p>
      *
      * @param srcChars the character array being tokenized, may be null.
      * @param offset   the start position within the character array, must be valid.
      * @param count    the number of characters to tokenize, must be valid.
      * @return The modifiable list of String tokens, unmodifiable if null array or zero count.
      */
     protected List<String> tokenize(final char[] srcChars, final int offset, final int count) {
         if (srcChars == null || count == 0) {
             return Collections.emptyList();
         }
         final TextStringBuilder buf = new TextStringBuilder();
         final List<String> tokenList = new ArrayList<>();
         int pos = offset;
         // loop around the entire buffer
         while (pos >= 0 && pos < count) {
             // find next token
             pos = readNextToken(srcChars, pos, count, buf, tokenList);
             // handle case where end of string is a delimiter
             if (pos >= count) {
                 addToken(tokenList, StringUtils.EMPTY);
             }
         }
         return tokenList;
     }
 
     /**
      * Gets the String content that the tokenizer is parsing.
      *
      * @return The string content being parsed.
      */
     @Override
     public String toString() {
         if (tokens == null) {
             return "StringTokenizer[not tokenized yet]";
         }
         return "StringTokenizer" + getTokenList();
     }
 }