Add Predicates

- Refactor to use Predicates,
- Explicitly test deprecated code

Author: garydgregory

src/changes/changes.xml

@@ -88,6 +88,7 @@ The <action> type attribute can be add,update,fix,remove.
     <action                   type="add" dev="ggregory" due-to="Gary Gregory">Add BasicThreadFactory.builder() and deprecate BasicThreadFactory.Builder().</action>
     <action                   type="add" dev="ggregory" due-to="Gary Gregory">Add BasicThreadFactory.daemon().</action>
     <action                   type="add" dev="ggregory" due-to="Gary Gregory">Add ArrayUtils.startsWith.</action>
+    <action                   type="add" dev="ggregory" due-to="Gary Gregory">Add Predicates.</action>
     <!-- UPDATE -->
     <action                   type="update" dev="ggregory" due-to="Gary Gregory, Dependabot">Bump org.apache.commons:commons-parent from 73 to 78 #1267, #1277, #1283, #1288, #1302.</action>
     <action                   type="update" dev="ggregory" due-to="Gary Gregory, Dependabot">[site] Bump org.codehaus.mojo:taglist-maven-plugin from 3.1.0 to 3.2.1 #1300.</action>

src/main/java/org/apache/commons/lang3/ThreadUtils.java

@@ -25,6 +25,7 @@
 import java.util.stream.Collectors;
 import java.util.stream.Stream;
 
+import org.apache.commons.lang3.function.Predicates;
 import org.apache.commons.lang3.time.DurationUtils;
 
 /**
@@ -170,13 +171,6 @@ public interface ThreadPredicate {
     @Deprecated
     public static final AlwaysTruePredicate ALWAYS_TRUE_PREDICATE = new AlwaysTruePredicate();
 
-    private static final Predicate<?> ALWAYS_TRUE = t -> true;
-
-    @SuppressWarnings("unchecked")
-    private static <T> Predicate<T> alwaysTruePredicate() {
-        return (Predicate<T>) ALWAYS_TRUE;
-    }
-
     /**
      * Finds the active thread with the specified id.
      *
@@ -478,7 +472,7 @@ public static Collection<Thread> findThreadsByName(final String threadName, fina
      *          thread groups from this thread's thread group up to the system thread group
      */
     public static Collection<ThreadGroup> getAllThreadGroups() {
-        return findThreadGroups(alwaysTruePredicate());
+        return findThreadGroups(Predicates.truePredicate());
     }
 
     /**
@@ -492,7 +486,7 @@ public static Collection<ThreadGroup> getAllThreadGroups() {
      *          thread groups from this thread's thread group up to the system thread group
      */
     public static Collection<Thread> getAllThreads() {
-        return findThreads(alwaysTruePredicate());
+        return findThreads(Predicates.truePredicate());
     }
 
     /**

src/main/java/org/apache/commons/lang3/function/Predicates.java

@@ -0,0 +1,62 @@
+/*
+ * 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.commons.lang3.function;
+
+import java.util.function.Predicate;
+
+/**
+ * Factory for {@link Predicate}.
+ *
+ * @since 3.18.0
+ */
+public class Predicates {
+
+    private static final Predicate<?> ALWAYS_TRUE = t -> true;
+    private static final Predicate<?> ALWAYS_FALSE = t -> false;
+
+    /**
+     * Returns the Predicate singleton that always returns false.
+     *
+     * @param <T> the type of the input to the predicate.
+     * @return the Predicate singleton.
+     */
+    @SuppressWarnings("unchecked")
+    // method name cannot be "false".
+    public static <T> Predicate<T> falsePredicate() {
+        return (Predicate<T>) ALWAYS_FALSE;
+    }
+
+    /**
+     * Returns the Predicate singleton that always returns true.
+     *
+     * @param <T> the type of the input to the predicate.
+     * @return the Predicate singleton.
+     */
+    @SuppressWarnings("unchecked")
+    // method name cannot be "true".
+    public static <T> Predicate<T> truePredicate() {
+        return (Predicate<T>) ALWAYS_TRUE;
+    }
+
+    /**
+     * No instances needed.
+     */
+    private Predicates() {
+        // empty
+    }
+}

src/test/java/org/apache/commons/lang3/ThreadUtilsTest.java

@@ -41,6 +41,7 @@
 
 import org.apache.commons.lang3.ThreadUtils.ThreadGroupPredicate;
 import org.apache.commons.lang3.ThreadUtils.ThreadPredicate;
+import org.apache.commons.lang3.function.Predicates;
 import org.junit.jupiter.api.Test;
 
 /**
@@ -125,7 +126,7 @@ public void testComplexThreadGroups() throws Exception {
             }
             assertThat("getAllThreadGroups", ThreadUtils.getAllThreadGroups().size(), greaterThanOrEqualTo(7));
             assertThat("getAllThreads", ThreadUtils.getAllThreads().size(), greaterThanOrEqualTo(11));
-            assertThat("findThreads(ThreadUtils.ALWAYS_TRUE_PREDICATE)", ThreadUtils.findThreads(ThreadUtils.ALWAYS_TRUE_PREDICATE).size(), greaterThanOrEqualTo(11));
+            assertThat("findThreads(ThreadUtils.ALWAYS_TRUE_PREDICATE)", ThreadUtils.findThreads(Predicates.truePredicate()).size(), greaterThanOrEqualTo(11));
             assertEquals(1, ThreadUtils.findThreadsByName(t4.getName(), threadGroup3.getName()).size());
             assertEquals(0, ThreadUtils.findThreadsByName(t4.getName(), threadGroup2.getName()).size());
             assertEquals(2, ThreadUtils.findThreadsByName(t11.getName(), threadGroup7.getName()).size());
@@ -152,6 +153,18 @@ public void testConstructor() {
         assertFalse(Modifier.isFinal(ThreadUtils.class.getModifiers()));
     }
 
+    @SuppressWarnings("deprecation")
+    @Test
+    public void testDepreacted() {
+        assertNotNull(ThreadUtils.ALWAYS_TRUE_PREDICATE);
+        ThreadPredicate tp = ThreadUtils.ALWAYS_TRUE_PREDICATE;
+        assertTrue(tp.test(null));
+        assertTrue(tp.test(new Thread()));
+        ThreadGroupPredicate tgp = ThreadUtils.ALWAYS_TRUE_PREDICATE;
+        assertTrue(tgp.test(null));
+        assertTrue(tgp.test(new ThreadGroup("")));
+    }
+
     @Test
     public void testGetAllThreadGroupsDoesNotReturnNull() {
         // LANG-1706 getAllThreadGroups and findThreadGroups should not return null items
@@ -299,8 +312,8 @@ public void testThreadGroupsByIdFail() {
 
     @Test
     public void testThreadGroupsNullParent() {
-        assertThrows(NullPointerException.class, () -> ThreadUtils.findThreadGroups(null, true, ThreadUtils.ALWAYS_TRUE_PREDICATE));
-        assertThrows(NullPointerException.class, () -> ThreadUtils.findThreadGroups(null, false, ThreadUtils.ALWAYS_TRUE_PREDICATE));
+        assertThrows(NullPointerException.class, () -> ThreadUtils.findThreadGroups(null, true, Predicates.truePredicate()));
+        assertThrows(NullPointerException.class, () -> ThreadUtils.findThreadGroups(null, false, Predicates.truePredicate()));
     }
 
     @Test

src/test/java/org/apache/commons/lang3/function/PredicatesTest.java

@@ -0,0 +1,49 @@
+/*
+ * 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.commons.lang3.function;
+
+import static org.junit.jupiter.api.Assertions.assertFalse;
+import static org.junit.jupiter.api.Assertions.assertTrue;
+
+import java.util.function.Predicate;
+
+import org.junit.jupiter.api.Test;
+
+/**
+ * Tests {@link Predicates}.
+ */
+public class PredicatesTest {
+
+    @Test
+    public void testFalsePredicate() {
+        assertFalse(Predicates.falsePredicate().test(null));
+        assertFalse(Predicates.falsePredicate().test(new Object()));
+        final Predicate<String> stringPredicate = Predicates.falsePredicate();
+        assertFalse(stringPredicate.test(null));
+        assertFalse(stringPredicate.test(""));
+    }
+
+    @Test
+    public void testTruePredicate() {
+        assertTrue(Predicates.truePredicate().test(null));
+        assertTrue(Predicates.truePredicate().test(new Object()));
+        final Predicate<String> stringPredicate = Predicates.truePredicate();
+        assertTrue(stringPredicate.test(null));
+        assertTrue(stringPredicate.test(""));
+    }
+}