CollectionUtil.java

/**
 * Copyright 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.
 */
package net.sf.katta.util;

import java.util.ArrayList;
import java.util.Collection;
import java.util.HashSet;
import java.util.List;
import java.util.Map;
import java.util.Set;

public class CollectionUtil {

  // TODO jz: avoid with bidi map?
  public static <K, V> Map<V, List<K>> invertListMap(Map<K, List<V>> key2ValuesMap) {
    One2ManyListMap<V, K> value2KeysMap = new One2ManyListMap<V, K>();
    for (K shardName : key2ValuesMap.keySet()) {
      List<V> nodes = key2ValuesMap.get(shardName);
      for (V node : nodes) {
        value2KeysMap.add(node, shardName);
      }
    }
    return value2KeysMap.asMap();
  }

  public static List<String> getListOfAdded(final Collection<String> oldList, final Collection<String> updatedList) {
    final List<String> addedEntriesList = new ArrayList<String>();
    extractAddedEntries(oldList, updatedList, addedEntriesList);
    return addedEntriesList;
  }

  public static Set<String> getSetOfAdded(final Collection<String> oldSet, final Collection<String> updatedSet) {
    final Set<String> addedEntriesSet = new HashSet<String>();
    extractAddedEntries(oldSet, updatedSet, addedEntriesSet);
    return addedEntriesSet;
  }

  public static List<String> getListOfRemoved(final Collection<String> oldList, final Collection<String> updatedList) {
    final List<String> removedEntriesList = new ArrayList<String>();
    extractRemovedEntries(oldList, updatedList, removedEntriesList);
    return removedEntriesList;
  }

  public static Set<String> getSetOfRemoved(final Collection<String> oldSet, final Collection<String> updatedSet) {
    final Set<String> removedEntriesSet = new HashSet<String>();
    extractRemovedEntries(oldSet, updatedSet, removedEntriesSet);
    return removedEntriesSet;
  }

  private final static void extractAddedEntries(final Collection<String> oldCollection,
          final Collection<String> updatedCollection, final Collection<String> addedEntriesCollection) {
    for (final String entry : updatedCollection) {
      if (!oldCollection.contains(entry)) {
        addedEntriesCollection.add(entry);
      }
    }
  }

  private static void extractRemovedEntries(final Collection<String> oldCollection,
          final Collection<String> updatedCollection, final Collection<String> removedEntriesCollection) {
    for (final String string : oldCollection) {
      if (!updatedCollection.contains(string)) {
        removedEntriesCollection.add(string);
      }
    }
  }

}