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Android example source code file (Pair.java)

This example Android source code file (Pair.java) is included in the DevDaily.com "Java Source Code Warehouse" project. The intent of this project is to help you "Learn Android by Example" TM.

Java - Android tags/keywords

a, b, classcastexception, f, pair, s

The Pair.java Android example source code

/*
 * Copyright (C) 2009 The Android Open Source Project
 *
 * 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 android.util;

/**
 * Container to ease passing around a tuple of two objects. This object provides a sensible
 * implementation of equals(), returning true if equals() is true on each of the contained
 * objects.
 */
public class Pair<F, S> {
    public final F first;
    public final S second;

    /**
     * Constructor for a Pair. If either are null then equals() and hashCode() will throw
     * a NullPointerException.
     * @param first the first object in the Pair
     * @param second the second object in the pair
     */
    public Pair(F first, S second) {
        this.first = first;
        this.second = second;
    }

    /**
     * Checks the two objects for equality by delegating to their respective equals() methods.
     * @param o the Pair to which this one is to be checked for equality
     * @return true if the underlying objects of the Pair are both considered equals()
     */
    public boolean equals(Object o) {
        if (o == this) return true;
        if (!(o instanceof Pair)) return false;
        final Pair<F, S> other;
        try {
            other = (Pair<F, S>) o;
        } catch (ClassCastException e) {
            return false;
        }
        return first.equals(other.first) && second.equals(other.second);
    }

    /**
     * Compute a hash code using the hash codes of the underlying objects
     * @return a hashcode of the Pair
     */
    public int hashCode() {
        int result = 17;
        result = 31 * result + first.hashCode();
        result = 31 * result + second.hashCode();
        return result;
    }

    /**
     * Convenience method for creating an appropriately typed pair.
     * @param a the first object in the Pair
     * @param b the second object in the pair
     * @return a Pair that is templatized with the types of a and b
     */
    public static <A, B> Pair  create(A a, B b) {
        return new Pair<A, B>(a, b);
    }
}

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