dist.edu.umd.cloud9.io.pair.PairOfWritables Maven / Gradle / Ivy

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University of Maryland's Hadoop Library
There is a newer version: 2.0.1
/*
 * Cloud9: A Hadoop toolkit for working with big data
 *
 * 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 edu.umd.cloud9.io.pair;

import java.io.DataInput;
import java.io.DataOutput;
import java.io.IOException;

import org.apache.hadoop.io.Writable;

/**
 * Class representing pair of Writables.
 */
public class PairOfWritables implements Writable {

	private L leftElement;
	private R rightElement;

	/**
	 * Creates a new PairOfWritables.
	 */
	public PairOfWritables() {}

	/**
	 * Creates a new PairOfWritables.
	 */
	public PairOfWritables(L left, R right) {
		leftElement = left;
		rightElement = right;
	}

	/**
	 * Deserializes the pair.
	 *
	 * @param in source for raw byte representation
	 */
	@Override @SuppressWarnings("unchecked")
	public void readFields(DataInput in) throws IOException {
		String keyClassName = in.readUTF();
		String valueClassName = in.readUTF();

		try {
			Class keyClass = (Class) Class.forName(keyClassName);
			leftElement = (L) keyClass.newInstance();
			Class valueClass = (Class) Class.forName(valueClassName);
			rightElement = (R) valueClass.newInstance();

			leftElement.readFields(in);
			rightElement.readFields(in);
		} catch (Exception e) {
			throw new RuntimeException("Unable to create PairOfWritables!");
		}
	}

	/**
	 * Serializes this pair.
	 *
	 * @param out where to write the raw byte representation
	 */
	@Override
	public void write(DataOutput out) throws IOException {
		out.writeUTF(leftElement.getClass().getCanonicalName());
		out.writeUTF(rightElement.getClass().getCanonicalName());

		leftElement.write(out);
		rightElement.write(out);
	}

	/**
	 * Returns the left element.
	 *
	 * @return the left element
	 */
	public L getLeftElement() {
		return leftElement;
	}

	/**
	 * Returns the right element.
	 *
	 * @return the right element
	 */
	public R getRightElement() {
		return rightElement;
	}

	/**
	 * Returns the key (left element).
	 *
	 * @return the key
	 */
	public L getKey() {
		return leftElement;
	}

	/**
	 * Returns the value (right element).
	 *
	 * @return the value
	 */
	public R getValue() {
		return rightElement;
	}

	/**
	 * Sets the right and left elements of this pair.
	 *
	 * @param left the left element
	 * @param right the right element
	 */
	public void set(L left, R right) {
		leftElement = left;
		rightElement = right;
	}

	/**
	 * Generates human-readable String representation of this pair.
	 *
	 * @return human-readable String representation of this pair
	 */
	public String toString() {
		return "(" + leftElement + ", " + rightElement + ")";
	}
}