Update #0 - First Release

sources/main/java/com/google/common/collect/DescendingMultiset.java

@@ -0,0 +1,151 @@
+/*
+ * Copyright (C) 2012 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 java.util.Comparator;
+import java.util.Iterator;
+import java.util.NavigableSet;
+import java.util.Set;
+
+import com.google.common.annotations.GwtCompatible;
+
+/**
+ * A skeleton implementation of a descending multiset. Only needs
+ * {@code forwardMultiset()} and {@code entryIterator()}.
+ * 
+ * @author Louis Wasserman
+ */
+@GwtCompatible(emulated = true)
+abstract class DescendingMultiset<E> extends ForwardingMultiset<E> implements SortedMultiset<E> {
+	abstract SortedMultiset<E> forwardMultiset();
+
+	private transient Comparator<? super E> comparator;
+
+	@Override
+	public Comparator<? super E> comparator() {
+		Comparator<? super E> result = comparator;
+		if (result == null) {
+			return comparator = Ordering.from(forwardMultiset().comparator()).<E>reverse();
+		}
+		return result;
+	}
+
+	private transient NavigableSet<E> elementSet;
+
+	@Override
+	public NavigableSet<E> elementSet() {
+		NavigableSet<E> result = elementSet;
+		if (result == null) {
+			return elementSet = new SortedMultisets.NavigableElementSet<E>(this);
+		}
+		return result;
+	}
+
+	@Override
+	public Entry<E> pollFirstEntry() {
+		return forwardMultiset().pollLastEntry();
+	}
+
+	@Override
+	public Entry<E> pollLastEntry() {
+		return forwardMultiset().pollFirstEntry();
+	}
+
+	@Override
+	public SortedMultiset<E> headMultiset(E toElement, BoundType boundType) {
+		return forwardMultiset().tailMultiset(toElement, boundType).descendingMultiset();
+	}
+
+	@Override
+	public SortedMultiset<E> subMultiset(E fromElement, BoundType fromBoundType, E toElement, BoundType toBoundType) {
+		return forwardMultiset().subMultiset(toElement, toBoundType, fromElement, fromBoundType).descendingMultiset();
+	}
+
+	@Override
+	public SortedMultiset<E> tailMultiset(E fromElement, BoundType boundType) {
+		return forwardMultiset().headMultiset(fromElement, boundType).descendingMultiset();
+	}
+
+	@Override
+	protected Multiset<E> delegate() {
+		return forwardMultiset();
+	}
+
+	@Override
+	public SortedMultiset<E> descendingMultiset() {
+		return forwardMultiset();
+	}
+
+	@Override
+	public Entry<E> firstEntry() {
+		return forwardMultiset().lastEntry();
+	}
+
+	@Override
+	public Entry<E> lastEntry() {
+		return forwardMultiset().firstEntry();
+	}
+
+	abstract Iterator<Entry<E>> entryIterator();
+
+	private transient Set<Entry<E>> entrySet;
+
+	@Override
+	public Set<Entry<E>> entrySet() {
+		Set<Entry<E>> result = entrySet;
+		return (result == null) ? entrySet = createEntrySet() : result;
+	}
+
+	Set<Entry<E>> createEntrySet() {
+		return new Multisets.EntrySet<E>() {
+			@Override
+			Multiset<E> multiset() {
+				return DescendingMultiset.this;
+			}
+
+			@Override
+			public Iterator<Entry<E>> iterator() {
+				return entryIterator();
+			}
+
+			@Override
+			public int size() {
+				return forwardMultiset().entrySet().size();
+			}
+		};
+	}
+
+	@Override
+	public Iterator<E> iterator() {
+		return Multisets.iteratorImpl(this);
+	}
+
+	@Override
+	public Object[] toArray() {
+		return standardToArray();
+	}
+
+	@Override
+	public <T> T[] toArray(T[] array) {
+		return standardToArray(array);
+	}
+
+	@Override
+	public String toString() {
+		return entrySet().toString();
+	}
+}