Polish "Use Comparable instead of dedicated implementations"

See gh-25478

spring-core/src/main/java/org/springframework/util/comparator/ComparableComparator.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2018 the original author or authors.
+ * Copyright 2002-2023 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -23,18 +23,17 @@
  * Mainly for internal use in other Comparators, when supposed
  * to work on Comparables.
  *
- * @deprecated use jdk-8 Comparator::naturalOrder
  * @author Keith Donald
  * @since 1.2.2
  * @param <T> the type of comparable objects that may be compared by this comparator
  * @see Comparable
+ * @deprecated as of 6.1 in favor of {@link Comparator#naturalOrder()}
  */
-@Deprecated
+@Deprecated(since = "6.1")
 public class ComparableComparator<T extends Comparable<T>> implements Comparator<T> {
 
 	/**
 	 * A shared instance of this default comparator.
-	 *
 	 * @see Comparators#comparable()
 	 */
 	@SuppressWarnings("rawtypes")

spring-core/src/main/java/org/springframework/util/comparator/Comparators.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2018 the original author or authors.
+ * Copyright 2002-2023 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -29,6 +29,7 @@ public abstract class Comparators {
 
 	/**
 	 * Return a {@link Comparable} adapter.
+	 * @see Comparator#naturalOrder()
 	 */
 	@SuppressWarnings("unchecked")
 	public static <T> Comparator<T> comparable() {
@@ -38,15 +39,16 @@ public static <T> Comparator<T> comparable() {
 	/**
 	 * Return a {@link Comparable} adapter which accepts
 	 * null values and sorts them lower than non-null values.
+	 * @see Comparator#nullsLast(Comparator)
 	 */
-	@SuppressWarnings("unchecked")
 	public static <T> Comparator<T> nullsLow() {
-		return (Comparator<T>) Comparator.nullsLast(Comparator.naturalOrder());
+		return nullsLow(comparable());
 	}
 
 	/**
 	 * Return a decorator for the given comparator which accepts
 	 * null values and sorts them lower than non-null values.
+	 * @see Comparator#nullsLast(Comparator)
 	 */
 	public static <T> Comparator<T> nullsLow(Comparator<T> comparator) {
 		return Comparator.nullsLast(comparator);
@@ -55,15 +57,16 @@ public static <T> Comparator<T> nullsLow(Comparator<T> comparator) {
 	/**
 	 * Return a {@link Comparable} adapter which accepts
 	 * null values and sorts them higher than non-null values.
+	 * @see Comparator#nullsFirst(Comparator)
 	 */
-	@SuppressWarnings("unchecked")
 	public static <T> Comparator<T> nullsHigh() {
-		return (Comparator<T>) Comparator.nullsFirst(Comparator.naturalOrder());
+		return nullsHigh(comparable());
 	}
 
 	/**
 	 * Return a decorator for the given comparator which accepts
 	 * null values and sorts them higher than non-null values.
+	 * @see Comparator#nullsFirst(Comparator)
 	 */
 	public static <T> Comparator<T> nullsHigh(Comparator<T> comparator) {
 		return Comparator.nullsFirst(comparator);

spring-core/src/main/java/org/springframework/util/comparator/NullSafeComparator.java

@@ -30,7 +30,10 @@
  * @since 1.2.2
  * @param <T> the type of objects that may be compared by this comparator
  * @see Comparable
+ * @see Comparators
+ * @deprecated as of 6.1 in favor of {@link Comparator#nullsLast} and {@link Comparator#nullsFirst}
  */
+@Deprecated(since = "6.1")
 public class NullSafeComparator<T> implements Comparator<T> {
 
 	/**
@@ -49,6 +52,7 @@ public class NullSafeComparator<T> implements Comparator<T> {
 	@SuppressWarnings("rawtypes")
 	public static final NullSafeComparator NULLS_HIGH = new NullSafeComparator<>(false);
 
+
 	private final Comparator<T> nonNullComparator;
 
 	private final boolean nullsLow;
@@ -68,9 +72,8 @@ public class NullSafeComparator<T> implements Comparator<T> {
 	 * @see #NULLS_LOW
 	 * @see #NULLS_HIGH
 	 */
-	@SuppressWarnings("unchecked")
 	private NullSafeComparator(boolean nullsLow) {
-		this.nonNullComparator = (Comparator<T>) Comparator.naturalOrder();
+		this.nonNullComparator = Comparators.comparable();
 		this.nullsLow = nullsLow;
 	}
 

spring-core/src/test/java/org/springframework/core/convert/converter/ConvertingComparatorTests.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2020 the original author or authors.
+ * Copyright 2002-2023 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -26,7 +26,7 @@
 
 import org.springframework.core.convert.ConversionService;
 import org.springframework.core.convert.support.DefaultConversionService;
-import org.springframework.util.comparator.ComparableComparator;
+import org.springframework.util.comparator.Comparators;
 
 import static org.assertj.core.api.Assertions.assertThat;
 import static org.assertj.core.api.Assertions.assertThatIllegalArgumentException;
@@ -95,17 +95,17 @@ private void testConversion(ConvertingComparator<String, Integer> convertingComp
 	}
 
 	@Test
-	void shouldGetMapEntryKeys() throws Exception {
+	void shouldGetMapEntryKeys() {
 		ArrayList<Entry<String, Integer>> list = createReverseOrderMapEntryList();
-		Comparator<Map.Entry<String, Integer>> comparator = ConvertingComparator.mapEntryKeys(new ComparableComparator<String>());
+		Comparator<Map.Entry<String, Integer>> comparator = ConvertingComparator.mapEntryKeys(Comparators.comparable());
 		list.sort(comparator);
 		assertThat(list.get(0).getKey()).isEqualTo("a");
 	}
 
 	@Test
-	void shouldGetMapEntryValues() throws Exception {
+	void shouldGetMapEntryValues() {
 		ArrayList<Entry<String, Integer>> list = createReverseOrderMapEntryList();
-		Comparator<Map.Entry<String, Integer>> comparator = ConvertingComparator.mapEntryValues(new ComparableComparator<Integer>());
+		Comparator<Map.Entry<String, Integer>> comparator = ConvertingComparator.mapEntryValues(Comparators.comparable());
 		list.sort(comparator);
 		assertThat(list.get(0).getValue()).isEqualTo(1);
 	}
@@ -130,7 +130,7 @@ public Integer convert(String source) {
 	}
 
 
-	private static class TestComparator extends ComparableComparator<Integer> {
+	private static class TestComparator implements Comparator<Integer> {
 
 		private boolean called;
 
@@ -139,7 +139,7 @@ public int compare(Integer o1, Integer o2) {
 			assertThat(o1).isInstanceOf(Integer.class);
 			assertThat(o2).isInstanceOf(Integer.class);
 			this.called = true;
-			return super.compare(o1, o2);
+			return Comparators.comparable().compare(o1, o2);
 		}
 
 		public void assertCalled() {

spring-core/src/test/java/org/springframework/util/ConcurrentReferenceHashMapTests.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2022 the original author or authors.
+ * Copyright 2002-2023 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -36,8 +36,7 @@
 import org.springframework.util.ConcurrentReferenceHashMap.Entry;
 import org.springframework.util.ConcurrentReferenceHashMap.Reference;
 import org.springframework.util.ConcurrentReferenceHashMap.Restructure;
-import org.springframework.util.comparator.ComparableComparator;
-import org.springframework.util.comparator.NullSafeComparator;
+import org.springframework.util.comparator.Comparators;
 
 import static org.assertj.core.api.Assertions.assertThat;
 import static org.assertj.core.api.Assertions.assertThatIllegalArgumentException;
@@ -51,8 +50,7 @@
  */
 class ConcurrentReferenceHashMapTests {
 
-	private static final Comparator<? super String> NULL_SAFE_STRING_SORT = new NullSafeComparator<>(
-			new ComparableComparator<String>(), true);
+	private static final Comparator<? super String> NULL_SAFE_STRING_SORT = Comparators.nullsLow();
 
 	private TestWeakConcurrentCache<Integer, String> map = new TestWeakConcurrentCache<>();
 

spring-core/src/test/java/org/springframework/util/comparator/BooleanComparatorTests.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2019 the original author or authors.
+ * Copyright 2002-2023 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.

spring-core/src/test/java/org/springframework/util/comparator/ComparableComparatorTests.java

@@ -30,6 +30,7 @@
  * @author Chris Beams
  * @author Phillip Webb
  */
+@Deprecated
 class ComparableComparatorTests {
 
 	@Test

spring-core/src/test/java/org/springframework/util/comparator/NullSafeComparatorTests.java

@@ -29,6 +29,7 @@
  * @author Chris Beams
  * @author Phillip Webb
  */
+@Deprecated
 class NullSafeComparatorTests {
 
 	@SuppressWarnings("unchecked")