Splits the provided text into an array with a maximum length, separators specified, preserving all tokens, including empty tokens created by adjacent separators. : String split « Data Type « Java

1. Java
2. Data Type
3. String split

Splits the provided text into an array with a maximum length, separators specified, preserving all tokens, including empty tokens created by adjacent separators.

     
/*
 * 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.
 */
import java.util.ArrayList;
import java.util.List;

public class Main {


  /**
   * <p>Splits the provided text into an array with a maximum length,
   * separators specified, preserving all tokens, including empty tokens 
   * created by adjacent separators.</p>
   *
   * <p>The separator is not included in the returned String array.
   * Adjacent separators are treated as separators for empty tokens.
   * Adjacent separators are treated as one separator.</p>
   *
   * <p>A <code>null</code> input String returns <code>null</code>.
   * A <code>null</code> separatorChars splits on whitespace.</p>
   *
   * <p>If more than <code>max</code> delimited substrings are found, the last
   * returned string includes all characters after the first <code>max - 1</code>
   * returned strings (including separator characters).</p>
   *
   * <pre>
   * StringUtils.splitPreserveAllTokens(null, *, *)            = null
   * StringUtils.splitPreserveAllTokens("", *, *)              = []
   * StringUtils.splitPreserveAllTokens("ab de fg", null, 0)   = ["ab", "cd", "ef"]
   * StringUtils.splitPreserveAllTokens("ab   de fg", null, 0) = ["ab", "cd", "ef"]
   * StringUtils.splitPreserveAllTokens("ab:cd:ef", ":", 0)    = ["ab", "cd", "ef"]
   * StringUtils.splitPreserveAllTokens("ab:cd:ef", ":", 2)    = ["ab", "cd:ef"]
   * StringUtils.splitPreserveAllTokens("ab   de fg", null, 2) = ["ab", "  de fg"]
   * StringUtils.splitPreserveAllTokens("ab   de fg", null, 3) = ["ab", "", " de fg"]
   * StringUtils.splitPreserveAllTokens("ab   de fg", null, 4) = ["ab", "", "", "de fg"]
   * </pre>
   *
   * @param str  the String to parse, may be <code>null</code>
   * @param separatorChars  the characters used as the delimiters,
   *  <code>null</code> splits on whitespace
   * @param max  the maximum number of elements to include in the
   *  array. A zero or negative value implies no limit
   * @return an array of parsed Strings, <code>null</code> if null String input
   * @since 2.1
   */
  public static String[] splitPreserveAllTokens(String str, String separatorChars, int max) {
      return splitWorker(str, separatorChars, max, true);
  }
  /**
   * Performs the logic for the <code>split</code> and 
   * <code>splitPreserveAllTokens</code> methods that return a maximum array 
   * length.
   *
   * @param str  the String to parse, may be <code>null</code>
   * @param separatorChars the separate character
   * @param max  the maximum number of elements to include in the
   *  array. A zero or negative value implies no limit.
   * @param preserveAllTokens if <code>true</code>, adjacent separators are
   * treated as empty token separators; if <code>false</code>, adjacent
   * separators are treated as one separator.
   * @return an array of parsed Strings, <code>null</code> if null String input
   */
  private static String[] splitWorker(String str, String separatorChars, int max, boolean preserveAllTokens) {
      // Performance tuned for 2.0 (JDK1.4)
      // Direct code is quicker than StringTokenizer.
      // Also, StringTokenizer uses isSpace() not isWhitespace()

      if (str == null) {
          return null;
      }
      int len = str.length();
      if (len == 0) {
          return new String[0];
      }
      List list = new ArrayList();
      int sizePlus1 = 1;
      int i = 0, start = 0;
      boolean match = false;
      boolean lastMatch = false;
      if (separatorChars == null) {
          // Null separator means use whitespace
          while (i < len) {
              if (Character.isWhitespace(str.charAt(i))) {
                  if (match || preserveAllTokens) {
                      lastMatch = true;
                      if (sizePlus1++ == max) {
                          i = len;
                          lastMatch = false;
                      }
                      list.add(str.substring(start, i));
                      match = false;
                  }
                  start = ++i;
                  continue;
              }
              lastMatch = false;
              match = true;
              i++;
          }
      } else if (separatorChars.length() == 1) {
          // Optimise 1 character case
          char sep = separatorChars.charAt(0);
          while (i < len) {
              if (str.charAt(i) == sep) {
                  if (match || preserveAllTokens) {
                      lastMatch = true;
                      if (sizePlus1++ == max) {
                          i = len;
                          lastMatch = false;
                      }
                      list.add(str.substring(start, i));
                      match = false;
                  }
                  start = ++i;
                  continue;
              }
              lastMatch = false;
              match = true;
              i++;
          }
      } else {
          // standard case
          while (i < len) {
              if (separatorChars.indexOf(str.charAt(i)) >= 0) {
                  if (match || preserveAllTokens) {
                      lastMatch = true;
                      if (sizePlus1++ == max) {
                          i = len;
                          lastMatch = false;
                      }
                      list.add(str.substring(start, i));
                      match = false;
                  }
                  start = ++i;
                  continue;
              }
              lastMatch = false;
              match = true;
              i++;
          }
      }
      if (match || (preserveAllTokens && lastMatch)) {
          list.add(str.substring(start, i));
      }
      return (String[]) list.toArray(new String[list.size()]);
  }

}

   
    
    
    
    
  

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