Update #0 - First Release

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

@@ -0,0 +1,71 @@
+/*
+ * 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 javax.annotation.Nullable;
+
+import com.google.common.annotations.GwtCompatible;
+import com.google.common.base.Function;
+import com.google.common.base.Objects;
+
+/**
+ * An ordering that orders elements by applying an order to the result of a
+ * function on those elements.
+ */
+@GwtCompatible(serializable = true)
+final class ByFunctionOrdering<F, T> extends Ordering<F> implements Serializable {
+	final Function<F, ? extends T> function;
+	final Ordering<T> ordering;
+
+	ByFunctionOrdering(Function<F, ? extends T> function, Ordering<T> ordering) {
+		this.function = checkNotNull(function);
+		this.ordering = checkNotNull(ordering);
+	}
+
+	@Override
+	public int compare(F left, F right) {
+		return ordering.compare(function.apply(left), function.apply(right));
+	}
+
+	@Override
+	public boolean equals(@Nullable Object object) {
+		if (object == this) {
+			return true;
+		}
+		if (object instanceof ByFunctionOrdering) {
+			ByFunctionOrdering<?, ?> that = (ByFunctionOrdering<?, ?>) object;
+			return this.function.equals(that.function) && this.ordering.equals(that.ordering);
+		}
+		return false;
+	}
+
+	@Override
+	public int hashCode() {
+		return Objects.hashCode(function, ordering);
+	}
+
+	@Override
+	public String toString() {
+		return ordering + ".onResultOf(" + function + ")";
+	}
+
+	private static final long serialVersionUID = 0;
+}