Update #0 - First Release

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

@@ -0,0 +1,99 @@
+/*
+ * Copyright (C) 2008 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.io.Serializable;
+import java.util.Map.Entry;
+
+import javax.annotation.Nullable;
+
+import com.google.common.annotations.GwtCompatible;
+import com.google.common.annotations.GwtIncompatible;
+
+/**
+ * {@code keySet()} implementation for {@link ImmutableMap}.
+ *
+ * @author Jesse Wilson
+ * @author Kevin Bourrillion
+ */
+@GwtCompatible(emulated = true)
+final class ImmutableMapKeySet<K, V> extends ImmutableSet<K> {
+	private final ImmutableMap<K, V> map;
+
+	ImmutableMapKeySet(ImmutableMap<K, V> map) {
+		this.map = map;
+	}
+
+	@Override
+	public int size() {
+		return map.size();
+	}
+
+	@Override
+	public UnmodifiableIterator<K> iterator() {
+		return asList().iterator();
+	}
+
+	@Override
+	public boolean contains(@Nullable Object object) {
+		return map.containsKey(object);
+	}
+
+	@Override
+	ImmutableList<K> createAsList() {
+		final ImmutableList<Entry<K, V>> entryList = map.entrySet().asList();
+		return new ImmutableAsList<K>() {
+
+			@Override
+			public K get(int index) {
+				return entryList.get(index).getKey();
+			}
+
+			@Override
+			ImmutableCollection<K> delegateCollection() {
+				return ImmutableMapKeySet.this;
+			}
+
+		};
+	}
+
+	@Override
+	boolean isPartialView() {
+		return true;
+	}
+
+	@GwtIncompatible("serialization")
+	@Override
+	Object writeReplace() {
+		return new KeySetSerializedForm<K>(map);
+	}
+
+	@GwtIncompatible("serialization")
+	private static class KeySetSerializedForm<K> implements Serializable {
+		final ImmutableMap<K, ?> map;
+
+		KeySetSerializedForm(ImmutableMap<K, ?> map) {
+			this.map = map;
+		}
+
+		Object readResolve() {
+			return map.keySet();
+		}
+
+		private static final long serialVersionUID = 0;
+	}
+}