A utility class for working with attribute and parameter collections used by Spring Web FLow : Collection « Collections Data Structure « Java

1. Java
2. Collections Data Structure
3. Collection

A utility class for working with attribute and parameter collections used by Spring Web FLow

    

/*
 * Copyright 2004-2008 the original author or authors.
 *
 * Licensed 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.io.Serializable;
import java.util.Collections;
import java.util.Enumeration;
import java.util.Iterator;
import java.util.List;

/**
 * A utility class for working with attribute and parameter collections used by Spring Web FLow.
 * 
 * @author Keith Donald
 * @author Erwin Vervaet
 */
public class CollectionUtils {

  /**
   * The shared, singleton empty iterator instance.
   */
  public static final Iterator EMPTY_ITERATOR = new EmptyIterator();

  /**
   * Private constructor to avoid instantiation.
   */
  private CollectionUtils() {
  }

  /**
   * Factory method that adapts an enumeration to an iterator.
   * @param enumeration the enumeration
   * @return the iterator
   */
  public static Iterator toIterator(Enumeration enumeration) {
    return new EnumerationIterator(enumeration);
  }


  /**
   * Add all given objects to given target list. No duplicates will be added. The contains() method of the given
   * target list will be used to determine whether or not an object is already in the list.
   * @param target the collection to which to objects will be added
   * @param objects the objects to add
   * @return whether or not the target collection changed
   */
  public static boolean addAllNoDuplicates(List target, Object[] objects) {
    if (objects == null || objects.length == 0) {
      return false;
    } else {
      boolean changed = false;
      for (int i = 0; i < objects.length; i++) {
        if (!target.contains(objects[i])) {
          target.add(objects[i]);
          changed = true;
        }
      }
      return changed;
    }
  }

  /**
   * Iterator iterating over no elements (hasNext() always returns false).
   */
  private static class EmptyIterator implements Iterator, Serializable {

    private EmptyIterator() {
    }

    public boolean hasNext() {
      return false;
    }

    public Object next() {
      throw new UnsupportedOperationException("There are no elements");
    }

    public void remove() {
      throw new UnsupportedOperationException("There are no elements");
    }
  }

  /**
   * Iterator wrapping an Enumeration.
   */
  private static class EnumerationIterator implements Iterator {

    private Enumeration enumeration;

    public EnumerationIterator(Enumeration enumeration) {
      this.enumeration = enumeration;
    }

    public boolean hasNext() {
      return enumeration.hasMoreElements();
    }

    public Object next() {
      return enumeration.nextElement();
    }

    public void remove() throws UnsupportedOperationException {
      throw new UnsupportedOperationException("Not supported");
    }
  }
}

   
    
    
    
  

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