org.apache.crunch.Pair.java Source code

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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.crunch;

import java.io.Serializable;

import com.google.common.collect.ComparisonChain;
import com.google.common.collect.Ordering;
import org.apache.commons.lang.builder.HashCodeBuilder;

/**
 * A convenience class for two-element {@link Tuple}s.
 */
public class Pair<K, V> implements Tuple, Comparable<Pair<K, V>>, Serializable {

    private final K first;
    private final V second;

    public static <T, U> Pair<T, U> of(T first, U second) {
        return new Pair<T, U>(first, second);
    }

    public Pair(K first, V second) {
        this.first = first;
        this.second = second;
    }

    public K first() {
        return first;
    }

    public V second() {
        return second;
    }

    public Object get(int index) {
        switch (index) {
        case 0:
            return first;
        case 1:
            return second;
        default:
            throw new ArrayIndexOutOfBoundsException();
        }
    }

    public int size() {
        return 2;
    }

    @Override
    public int hashCode() {
        HashCodeBuilder hcb = new HashCodeBuilder();
        return hcb.append(first).append(second).toHashCode();
    }

    @Override
    public boolean equals(Object obj) {
        if (this == obj)
            return true;
        if (obj == null)
            return false;
        if (getClass() != obj.getClass())
            return false;
        Pair<?, ?> other = (Pair<?, ?>) obj;
        return (first == other.first || (first != null && first.equals(other.first)))
                && (second == other.second || (second != null && second.equals(other.second)));
    }

    @Override
    public String toString() {
        StringBuilder sb = new StringBuilder("[");
        sb.append(first).append(",").append(second).append("]");
        return sb.toString();
    }

    private int cmp(Object lhs, Object rhs) {
        if (lhs == rhs) {
            return 0;
        } else if (lhs != null && Comparable.class.isAssignableFrom(lhs.getClass())) {
            return Ordering.natural().nullsLast().compare((Comparable) lhs, (Comparable) rhs);//(Comparable) lhs).compareTo(rhs);
        }
        if (lhs == null) {
            return 1; // nulls last
        }
        if (rhs == null) {
            return -1; // nulls last
        }
        if (lhs.equals(rhs)) {
            return 0;
        }

        // Now we compare based on hash code. We already know that the two sides are not equal, so
        // if the hash codes are equal, we just use arbitrary (but consistent) ordering
        return ComparisonChain.start().compare(lhs.hashCode(), rhs.hashCode())
                .compare(lhs, rhs, Ordering.arbitrary()).result();
    }

    @Override
    public int compareTo(Pair<K, V> o) {
        int diff = cmp(first, o.first);
        if (diff == 0) {
            diff = cmp(second, o.second);
        }
        return diff;
    }
}