org.jasig.ssp.util.collections.Pair.java Source code

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Here is the source code for org.jasig.ssp.util.collections.Pair.java

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/**
 * Licensed to Apereo under one or more contributor license
 * agreements. See the NOTICE file distributed with this work
 * for additional information regarding copyright ownership.
 * Apereo 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 the following location:
 *
 *   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.jasig.ssp.util.collections;

import com.google.common.collect.Maps;
import org.codehaus.jackson.annotate.JsonCreator;
import org.codehaus.jackson.annotate.JsonProperty;

import java.util.Map;

/**
 * A pair of two data items, a.k.a. a binary tuple.
 * 
 * <p>
 * Argument types must be immutable, or at least ensure that all consumers do
 * not modify the values.
 * 
 * @author lew@lewscanon.com
 * @param <T>
 *            First argument type, must be an immutable type or a mutable type
 *            that is never modified
 * @param <U>
 *            Second argument type, must be an immutable type or a mutable type
 *            that is never modified
 */
public class Pair<T, U> {
    private final T first;

    private final U second;

    private transient final int hash;

    /**
     * Construct a Pair with the specified arguments.
     * 
     * @param f
     *            first argument
     * @param s
     *            second argument
     */
    @JsonCreator
    public Pair(@JsonProperty("first") final T f, @JsonProperty("second") final U s) {
        this.first = f;
        this.second = s;
        hash = (first == null ? 0 : first.hashCode() * 31) + (second == null ? 0 : second.hashCode());
    }

    /**
     * Gets the first argument
     * 
     * @return the first argument
     */
    public T getFirst() {
        return first;
    }

    /**
     * Gets the second argument
     * 
     * @return the second argument
     */
    public U getSecond() {
        return second;
    }

    @Override
    public int hashCode() {
        return hash;
    }

    @Override
    public boolean equals(final Object obj) {
        if (this == obj) {
            return true;
        }

        if (!(Pair.class.isInstance(obj)) || !(getClass().equals(obj.getClass()))) {
            return false;
        }

        // class cast checked in preceding block
        @SuppressWarnings("unchecked")
        final Pair<T, U> other = getClass().cast(obj);

        return (first == null ? other.first == null : first.equals(other.first))
                && (second == null ? other.second == null : second.equals(other.second));
    }

    public Map<T, U> toMap() {
        Map<T, U> map = Maps.newHashMapWithExpectedSize(1);
        map.put(first, second);
        return map;
    }
}