Converts array into a java.util.Map. : Customized Map « Collections « Java Tutorial

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import java.util.HashMap;
import java.util.Map;

/* 
 * 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.
 *
 *
 */


/**
 * @author Stephen Colebourne
 * @author Moritz Petersen
 * @author <a href="mailto:fredrik@westermarck.com">Fredrik Westermarck</a>
 * @author Nikolay Metchev
 * @author Matthew Hawthorne
 * @author Tim O'Brien
 * @author Pete Gieser
 * @author Gary Gregory
 * @author <a href="mailto:equinus100@hotmail.com">Ashwin S</a>
 * @author Maarten Coene
 * @since 2.0
 * @version $Id: ArrayUtils.java 632503 2008-03-01 00:21:52Z ggregory $
 */
public class Main {

  // To map
  //-----------------------------------------------------------------------
  /**
   * Converts the given array into a {@link java.util.Map}. Each element of the array
   * must be either a {@link java.util.Map.Entry} or an Array, containing at least two
   * elements, where the first element is used as key and the second as
   * value.
   *
   * This method can be used to initialize:
   * <pre>
   * // Create a Map mapping colors.
   * Map colorMap = MapUtils.toMap(new String[][] {{
   *     {"RED", "#FF0000"},
   *     {"GREEN", "#00FF00"},
   *     {"BLUE", "#0000FF"}});
   * </pre>
   * 
   * This method returns <code>null</code> for a <code>null</code> input array.
   *
   * @param array  an array whose elements are either a {@link java.util.Map.Entry} or
   *  an Array containing at least two elements, may be <code>null</code>
   * @return a <code>Map</code> that was created from the array
   * @throws IllegalArgumentException  if one element of this Array is
   *  itself an Array containing less then two elements
   * @throws IllegalArgumentException  if the array contains elements other
   *  than {@link java.util.Map.Entry} and an Array
   */
  public static Map toMap(Object[] array) {
      if (array == null) {
          return null;
      }
      final Map map = new HashMap((int) (array.length * 1.5));
      for (int i = 0; i < array.length; i++) {
          Object object = array[i];
          if (object instanceof Map.Entry) {
              Map.Entry entry = (Map.Entry) object;
              map.put(entry.getKey(), entry.getValue());
          } else if (object instanceof Object[]) {
              Object[] entry = (Object[]) object;
              if (entry.length < 2) {
                  throw new IllegalArgumentException("Array element " + i + ", '"
                      + object
                      + "', has a length less than 2");
              }
              map.put(entry[0], entry[1]);
          } else {
              throw new IllegalArgumentException("Array element " + i + ", '"
                      + object
                      + "', is neither of type Map.Entry nor an Array");
          }
      }
      return map;
  }
}