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/*
 *  Copyright (c) 2018 Uber Technologies, Inc. ([email protected])
 *
 *  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 com.uber.hoodie.common.util.collection;

/**
 * (NOTE: Adapted from Apache commons-lang3)
 * An immutable pair consisting of two {@code Object} elements.
 *
 * Although the implementation is immutable, there is no restriction on the objects
 * that may be stored. If mutable objects are stored in the pair, then the pair
 * itself effectively becomes mutable. The class is also {@code final}, so a subclass
 * can not add undesirable behaviour.
 *
 * #ThreadSafe# if both paired objects are thread-safe
 *
 * @param  the left element type
 * @param  the right element type
 */
public final class ImmutablePair extends Pair {

  /**
   * Serialization version
   */
  private static final long serialVersionUID = 4954918890077093841L;

  /**
   * Left object
   */
  public final L left;
  /**
   * Right object
   */
  public final R right;

  /**
   * Obtains an immutable pair of from two objects inferring the generic types.
   *
   * This factory allows the pair to be created using inference to
   * obtain the generic types.
   *
   * @param  the left element type
   * @param  the right element type
   * @param left the left element, may be null
   * @param right the right element, may be null
   * @return a pair formed from the two parameters, not null
   */
  public static  ImmutablePair of(final L left, final R right) {
    return new ImmutablePair(left, right);
  }

  /**
   * Create a new pair instance.
   *
   * @param left the left value, may be null
   * @param right the right value, may be null
   */
  public ImmutablePair(final L left, final R right) {
    super();
    this.left = left;
    this.right = right;
  }

  //-----------------------------------------------------------------------

  /**
   * {@inheritDoc}
   */
  @Override
  public L getLeft() {
    return left;
  }

  /**
   * {@inheritDoc}
   */
  @Override
  public R getRight() {
    return right;
  }

  /**
   * Throws {@code UnsupportedOperationException}.
   *
   * This pair is immutable, so this operation is not supported.
   *
   * @param value the value to set
   * @return never
   * @throws UnsupportedOperationException as this operation is not supported
   */
  @Override
  public R setValue(final R value) {
    throw new UnsupportedOperationException();
  }

}