org.apache.giraph.utils.CollectionUtils.java Source code

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Here is the source code for org.apache.giraph.utils.CollectionUtils.java

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/*
 * 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.
 */

package org.apache.giraph.utils;

import com.google.common.collect.Iterables;
import java.util.Collection;
import java.util.Iterator;
import java.util.concurrent.ConcurrentMap;
import org.apache.log4j.Logger;

/** Helper methods for Collections */
public class CollectionUtils {
    /** Class logger */
    private static final Logger LOG = Logger.getLogger(CollectionUtils.class);

    /** Do not instantiate. */
    private CollectionUtils() {
    }

    /**
     * If map already has a value associated with the key it adds values to that
     * value, otherwise it will put values to the map.  Do not reuse values.
     *
     * @param key    Key under which we are adding values
     * @param values Values we want to add
     * @param map    Map which we are adding values to
     * @param <K> Key
     * @param <V> Value
     * @param <C> Collection
     * @return New value associated with the key
     */
    public static <K, V, C extends Collection<V>> C addConcurrent(K key, C values, ConcurrentMap<K, C> map) {
        C currentValues = map.get(key);
        if (currentValues == null) {
            currentValues = map.putIfAbsent(key, values);
            if (currentValues == null) {
                return values;
            }
        }
        synchronized (currentValues) {
            currentValues.addAll(values);
        }
        return currentValues;
    }

    /**
     * Helper method to check if iterables are equal.  Supports the case
     * where the iterable next() returns a reused object.  We do assume that
     * iterator() produces the objects in the same order across repeated calls,
     * if the object doesn't change.   This is very expensive (n^2) and should
     * be used for testing only.
     *
     * @param first First iterable
     * @param second Second iterable
     * @param <T> Type to compare
     * @return True if equal, false otherwise
     */
    public static <T> boolean isEqual(Iterable<T> first, Iterable<T> second) {
        // Relies on elements from the iterator arriving in the same order.
        // For every element in first, check elements on the second iterable by
        // marking the ones seen that have been found.  Then ensure that all
        // the elements of the second have been seen as well.
        int firstSize = Iterables.size(first);
        int secondSize = Iterables.size(second);
        boolean[] usedSecondArray = new boolean[secondSize];
        Iterator<T> firstIterator = first.iterator();
        while (firstIterator.hasNext()) {
            T firstValue = firstIterator.next();
            boolean foundFirstValue = false;
            Iterator<T> secondIterator = second.iterator();
            for (int i = 0; i < usedSecondArray.length; ++i) {
                T secondValue = secondIterator.next();
                if (!usedSecondArray[i]) {
                    if (firstValue.equals(secondValue)) {
                        usedSecondArray[i] = true;
                        foundFirstValue = true;
                        break;
                    }
                }
            }

            if (!foundFirstValue) {
                LOG.error("isEqual: Couldn't find element from first (" + firstValue + ") in second " + second
                        + "(size=" + secondSize + ")");
                return false;
            }
        }

        Iterator<T> secondIterator = second.iterator();
        for (int i = 0; i < usedSecondArray.length; ++i) {
            T secondValue = secondIterator.next();
            if (!usedSecondArray[i]) {
                LOG.error("isEqual: Element " + secondValue + " (index " + i + ") in second " + second + "(size="
                        + secondSize + ") not found in " + first + " (size=" + firstSize + ")");
                return false;
            }
        }

        return true;
    }
}