je-ik commented on code in PR #32074:
URL: https://github.com/apache/beam/pull/32074#discussion_r1714090124
##########
sdks/java/core/src/main/java/org/apache/beam/sdk/transforms/SerializableComparator.java:
##########
@@ -19,10 +19,29 @@
import java.io.Serializable;
import java.util.Comparator;
+import java.util.Objects;
+import java.util.function.Function;
/**
* A {@code Comparator} that is also {@code Serializable}.
*
* @param <T> type of values being compared
*/
-public interface SerializableComparator<T> extends Comparator<T>, Serializable
{}
+public interface SerializableComparator<T> extends Comparator<T>, Serializable
{
+ /**
+ * Analogous to {@link Comparator#comparing(Function)}, except that it takes
in a {@link
+ * SerializableFunction} as the key extractor and returns a {@link
SerializableComparator}.
+ *
+ * @param keyExtractor the function used to extract the {@link
java.lang.Comparable} sort key
+ * @return A {@link SerializableComparator} that compares by an extracted key
+ * @param <T> the type of element to be compared
+ * @param <V> the type of the {@code Comparable} sort key
+ * @see Comparator#comparing(Function)
+ */
+ static <T, V extends Comparable<? super V>> SerializableComparator<T>
comparing(
Review Comment:
I wonder, why `? super V` and not using `V` directly? Does it have any
advantages?
##########
sdks/java/core/src/main/java/org/apache/beam/sdk/transforms/SerializableComparator.java:
##########
@@ -19,10 +19,29 @@
import java.io.Serializable;
import java.util.Comparator;
+import java.util.Objects;
+import java.util.function.Function;
/**
* A {@code Comparator} that is also {@code Serializable}.
*
* @param <T> type of values being compared
*/
-public interface SerializableComparator<T> extends Comparator<T>, Serializable
{}
+public interface SerializableComparator<T> extends Comparator<T>, Serializable
{
+ /**
+ * Analogous to {@link Comparator#comparing(Function)}, except that it takes
in a {@link
+ * SerializableFunction} as the key extractor and returns a {@link
SerializableComparator}.
+ *
+ * @param keyExtractor the function used to extract the {@link
java.lang.Comparable} sort key
+ * @return A {@link SerializableComparator} that compares by an extracted key
+ * @param <T> the type of element to be compared
+ * @param <V> the type of the {@code Comparable} sort key
+ * @see Comparator#comparing(Function)
+ */
+ static <T, V extends Comparable<? super V>> SerializableComparator<T>
comparing(
+ SerializableFunction<? super T, ? extends V> keyExtractor) {
Review Comment:
Same here probably for `T`?
##########
sdks/java/core/src/test/java/org/apache/beam/sdk/transforms/SerializableComparatorTest.java:
##########
@@ -0,0 +1,38 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements. See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership. The ASF licenses this file
+ * to you 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 org.apache.beam.sdk.transforms;
+
+import java.io.Serializable;
+import org.junit.Assert;
+import org.junit.Test;
+import org.junit.runner.RunWith;
+import org.junit.runners.JUnit4;
+
+/** Tests for {@link SerializableComparator}. */
+@RunWith(JUnit4.class)
+public class SerializableComparatorTest {
+
+ /** Basic test of {@link SerializableComparator} being {@link
java.io.Serializable}. */
+ @Test
+ public void testIfImplementsSerializable() {
+ SerializableFunction<String, Integer> fn = Integer::parseInt;
+
+ SerializableComparator<String> cmp = SerializableComparator.comparing(fn);
+ Assert.assertTrue(cmp instanceof Serializable);
Review Comment:
This does not imply that the instance can be serialized. It would be better
to use the `SerializableUtils` to check the serialization and deserialization.
##########
sdks/java/core/src/test/java/org/apache/beam/sdk/transforms/SerializableComparatorTest.java:
##########
@@ -0,0 +1,38 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements. See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership. The ASF licenses this file
+ * to you 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 org.apache.beam.sdk.transforms;
+
+import java.io.Serializable;
+import org.junit.Assert;
+import org.junit.Test;
+import org.junit.runner.RunWith;
+import org.junit.runners.JUnit4;
+
+/** Tests for {@link SerializableComparator}. */
+@RunWith(JUnit4.class)
+public class SerializableComparatorTest {
+
+ /** Basic test of {@link SerializableComparator} being {@link
java.io.Serializable}. */
+ @Test
+ public void testIfImplementsSerializable() {
+ SerializableFunction<String, Integer> fn = Integer::parseInt;
+
+ SerializableComparator<String> cmp = SerializableComparator.comparing(fn);
+ Assert.assertTrue(cmp instanceof Serializable);
Review Comment:
You could have left the original tests as well, those were fine.
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