Update #0 - First Release

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

@@ -0,0 +1,57 @@
+/*
+ * Copyright (C) 2007 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 static com.google.common.base.Preconditions.checkNotNull;
+
+import java.io.Serializable;
+
+import com.google.common.annotations.GwtCompatible;
+
+/** An ordering that uses the natural order of the values. */
+@GwtCompatible(serializable = true)
+@SuppressWarnings("unchecked") // TODO(kevinb): the right way to explain this??
+final class NaturalOrdering extends Ordering<Comparable> implements Serializable {
+	static final NaturalOrdering INSTANCE = new NaturalOrdering();
+
+	@Override
+	public int compare(Comparable left, Comparable right) {
+		checkNotNull(left); // for GWT
+		checkNotNull(right);
+		return left.compareTo(right);
+	}
+
+	@Override
+	public <S extends Comparable> Ordering<S> reverse() {
+		return (Ordering<S>) ReverseNaturalOrdering.INSTANCE;
+	}
+
+	// preserving singleton-ness gives equals()/hashCode() for free
+	private Object readResolve() {
+		return INSTANCE;
+	}
+
+	@Override
+	public String toString() {
+		return "Ordering.natural()";
+	}
+
+	private NaturalOrdering() {
+	}
+
+	private static final long serialVersionUID = 0;
+}