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/**
 * Copyright (C) 2006-2015 phloc systems
 * http://www.phloc.com
 * office[at]phloc[dot]com
 *
 * 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.phloc.commons.collections.pair;

import javax.annotation.Nonnull;
import javax.annotation.Nullable;
import javax.annotation.concurrent.NotThreadSafe;

import com.phloc.commons.ValueEnforcer;
import com.phloc.commons.equals.EqualsUtils;
import com.phloc.commons.hash.HashCodeGenerator;
import com.phloc.commons.state.EChange;
import com.phloc.commons.string.ToStringGenerator;

/**
 * A generic pair class. It wraps two objects of arbitrary type. If you just
 * want to wrap a single object, look at class
 * {@link com.phloc.commons.mutable.Wrapper}.
 * 
 * @author Philip Helger
 * @param 
 *        First type.
 * @param 
 *        Second type.
 */
@NotThreadSafe
public final class Pair  implements IPair 
{
  private DATA1TYPE m_aFirst;
  private DATA2TYPE m_aSecond;

  public Pair ()
  {
    this (null, null);
  }

  public  Pair (@Nullable final T2 aFirst, @Nullable final U2 aSecond)
  {
    m_aFirst = aFirst;
    m_aSecond = aSecond;
  }

  public Pair (@Nonnull final IReadonlyPair  rhs)
  {
    ValueEnforcer.notNull (rhs, "Pair");
    m_aFirst = rhs.getFirst ();
    m_aSecond = rhs.getSecond ();
  }

  @Nullable
  public DATA1TYPE getFirst ()
  {
    return m_aFirst;
  }

  @Nonnull
  public EChange setFirst (@Nullable final DATA1TYPE aFirst)
  {
    if (EqualsUtils.equals (aFirst, m_aFirst))
      return EChange.UNCHANGED;
    m_aFirst = aFirst;
    return EChange.CHANGED;
  }

  @Nullable
  public DATA2TYPE getSecond ()
  {
    return m_aSecond;
  }

  @Nonnull
  public EChange setSecond (@Nullable final DATA2TYPE aSecond)
  {
    if (EqualsUtils.equals (aSecond, m_aSecond))
      return EChange.UNCHANGED;
    m_aSecond = aSecond;
    return EChange.CHANGED;
  }

  @Override
  public boolean equals (final Object o)
  {
    if (o == this)
      return true;
    if (!(o instanceof Pair ))
      return false;
    final Pair  rhs = (Pair ) o;
    return EqualsUtils.equals (m_aFirst, rhs.m_aFirst) && EqualsUtils.equals (m_aSecond, rhs.m_aSecond);
  }

  @Override
  public int hashCode ()
  {
    return new HashCodeGenerator (this).append (m_aFirst).append (m_aSecond).getHashCode ();
  }

  @Override
  public String toString ()
  {
    return new ToStringGenerator (null).append ("first", m_aFirst).append ("second", m_aSecond).toString ();
  }

  @Nonnull
  public static  IPair  create (@Nullable final T aFirst, @Nullable final U aSecond)
  {
    return new Pair  (aFirst, aSecond);
  }
}