/*
 * Copyright (C) 2011 The Guava Authors
 *
 * 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.google.common.collect;

import com.google.common.annotations.GwtCompatible;
import java.util.Collection;
import java.util.Comparator;
import java.util.Iterator;
import java.util.NavigableSet;
import java.util.Set;

A Multiset which maintains the ordering of its elements, according to either their natural order or an explicit Comparator. This order is reflected when iterating over the sorted multiset, either directly, or through its elementSet or entrySet views. In all cases, this implementation uses Comparable.compareTo or Comparator.compare instead of Object.equals to determine equivalence of instances. 
Warning: The comparison must be consistent with equals as explained by the Comparable class specification. Otherwise, the resulting multiset will violate the Collection contract, which it is specified in terms of Object.equals. 
See the Guava User Guide article on  
Multiset.
Author:
Louis Wasserman
Since:
11.0/**
 * A {@link Multiset} which maintains the ordering of its elements, according to either their
 * natural order or an explicit {@link Comparator}. This order is reflected when iterating over the
 * sorted multiset, either directly, or through its {@code elementSet} or {@code entrySet} views. In
 * all cases, this implementation uses {@link Comparable#compareTo} or {@link Comparator#compare}
 * instead of {@link Object#equals} to determine equivalence of instances.
 *
 * <p><b>Warning:</b> The comparison must be <i>consistent with equals</i> as explained by the
 * {@link Comparable} class specification. Otherwise, the resulting multiset will violate the {@link
 * Collection} contract, which it is specified in terms of {@link Object#equals}.
 *
 * <p>See the Guava User Guide article on <a href=
 * "https://github.com/google/guava/wiki/NewCollectionTypesExplained#multiset"> {@code
 * Multiset}</a>.
 *
 * @author Louis Wasserman
 * @since 11.0
 */
@GwtCompatible(emulated = true)
public interface SortedMultiset<E> extends SortedMultisetBridge<E>, SortedIterable<E> {
  
Returns the comparator that orders this multiset, or Ordering.natural() if the natural ordering of the elements is used. /**
   * Returns the comparator that orders this multiset, or {@link Ordering#natural()} if the natural
   * ordering of the elements is used.
   */
  @Override
  Comparator<? super E> comparator();

  
Returns the entry of the first element in this multiset, or null if this multiset is empty. /**
   * Returns the entry of the first element in this multiset, or {@code null} if this multiset is
   * empty.
   */
  Entry<E> firstEntry();

  
Returns the entry of the last element in this multiset, or null if this multiset is empty. /**
   * Returns the entry of the last element in this multiset, or {@code null} if this multiset is
   * empty.
   */
  Entry<E> lastEntry();

  
Returns and removes the entry associated with the lowest element in this multiset, or returns null if this multiset is empty. /**
   * Returns and removes the entry associated with the lowest element in this multiset, or returns
   * {@code null} if this multiset is empty.
   */
  Entry<E> pollFirstEntry();

  
Returns and removes the entry associated with the greatest element in this multiset, or returns null if this multiset is empty. /**
   * Returns and removes the entry associated with the greatest element in this multiset, or returns
   * {@code null} if this multiset is empty.
   */
  Entry<E> pollLastEntry();

  
Returns a NavigableSet view of the distinct elements in this multiset. 
Since:
14.0 (present with return type SortedSet since 11.0)/**
   * Returns a {@link NavigableSet} view of the distinct elements in this multiset.
   *
   * @since 14.0 (present with return type {@code SortedSet} since 11.0)
   */
  @Override
  NavigableSet<E> elementSet();

  
{@inheritDoc}
The entrySet's iterator returns entries in ascending element order according to the this multiset's comparator. /**
   * {@inheritDoc}
   *
   * <p>The {@code entrySet}'s iterator returns entries in ascending element order according to the
   * this multiset's comparator.
   */
  @Override
  Set<Entry<E>> entrySet();

  
{@inheritDoc}
The iterator returns the elements in ascending order according to this multiset's
comparator.
/**
   * {@inheritDoc}
   *
   * <p>The iterator returns the elements in ascending order according to this multiset's
   * comparator.
   */
  @Override
  Iterator<E> iterator();

  
Returns a descending view of this multiset. Modifications made to either map will be reflected
in the other.
/**
   * Returns a descending view of this multiset. Modifications made to either map will be reflected
   * in the other.
   */
  SortedMultiset<E> descendingMultiset();

  
Returns a view of this multiset restricted to the elements less than upperBound, optionally including upperBound itself. The returned multiset is a view of this multiset, so changes to one will be reflected in the other. The returned multiset supports all operations that this multiset supports. 
The returned multiset will throw an IllegalArgumentException on attempts to add elements outside its range. /**
   * Returns a view of this multiset restricted to the elements less than {@code upperBound},
   * optionally including {@code upperBound} itself. The returned multiset is a view of this
   * multiset, so changes to one will be reflected in the other. The returned multiset supports all
   * operations that this multiset supports.
   *
   * <p>The returned multiset will throw an {@link IllegalArgumentException} on attempts to add
   * elements outside its range.
   */
  SortedMultiset<E> headMultiset(E upperBound, BoundType boundType);

  
Returns a view of this multiset restricted to the range between lowerBound and 
upperBound. The returned multiset is a view of this multiset, so changes to one will be reflected in the other. The returned multiset supports all operations that this multiset supports. 
The returned multiset will throw an IllegalArgumentException on attempts to add elements outside its range. 
This method is equivalent to tailMultiset(lowerBound,
lowerBoundType).headMultiset(upperBound, upperBoundType). /**
   * Returns a view of this multiset restricted to the range between {@code lowerBound} and {@code
   * upperBound}. The returned multiset is a view of this multiset, so changes to one will be
   * reflected in the other. The returned multiset supports all operations that this multiset
   * supports.
   *
   * <p>The returned multiset will throw an {@link IllegalArgumentException} on attempts to add
   * elements outside its range.
   *
   * <p>This method is equivalent to {@code tailMultiset(lowerBound,
   * lowerBoundType).headMultiset(upperBound, upperBoundType)}.
   */
  SortedMultiset<E> subMultiset(
      E lowerBound, BoundType lowerBoundType, E upperBound, BoundType upperBoundType);

  
Returns a view of this multiset restricted to the elements greater than lowerBound, optionally including lowerBound itself. The returned multiset is a view of this multiset, so changes to one will be reflected in the other. The returned multiset supports all operations that this multiset supports. 
The returned multiset will throw an IllegalArgumentException on attempts to add elements outside its range. /**
   * Returns a view of this multiset restricted to the elements greater than {@code lowerBound},
   * optionally including {@code lowerBound} itself. The returned multiset is a view of this
   * multiset, so changes to one will be reflected in the other. The returned multiset supports all
   * operations that this multiset supports.
   *
   * <p>The returned multiset will throw an {@link IllegalArgumentException} on attempts to add
   * elements outside its range.
   */
  SortedMultiset<E> tailMultiset(E lowerBound, BoundType boundType);
}