Splits the provided text into an array, using whitespace as the separator, 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, using whitespace as the separator, 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, using whitespace as the
   * separator, preserving all tokens, including empty tokens created by 
   * adjacent separators. This is an alternative to using StringTokenizer.
   * Whitespace is defined by {@link Character#isWhitespace(char)}.</p>
   *
   * <p>The separator is not included in the returned String array.
   * Adjacent separators are treated as separators for empty tokens.
   * For more control over the split use the StrTokenizer class.</p>
   *
   * <p>A <code>null</code> input String returns <code>null</code>.</p>
   *
   * <pre>
   * StringUtils.splitPreserveAllTokens(null)       = null
   * StringUtils.splitPreserveAllTokens("")         = []
   * StringUtils.splitPreserveAllTokens("abc def")  = ["abc", "def"]
   * StringUtils.splitPreserveAllTokens("abc  def") = ["abc", "", "def"]
   * StringUtils.splitPreserveAllTokens(" abc ")    = ["", "abc", ""]
   * </pre>
   *
   * @param str  the String to parse, may be <code>null</code>
   * @return an array of parsed Strings, <code>null</code> if null String input
   * @since 2.1
   */
  public static String[] splitPreserveAllTokens(String str) {
      return splitWorker(str, null, -1, 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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