Add Memoizer(Function) and Memoizer(Function, boolean).

src/changes/changes.xml

@@ -123,6 +123,7 @@ The <action> type attribute can be add,update,fix,remove.
     <action                   type="add" dev="ggregory" due-to="Gary Gregory">Add JavaVersion.JAVA_18.</action>
     <action                   type="add" dev="ggregory" due-to="Gary Gregory">Add TimeZones.toTimeZone(TimeZone).</action>
     <action                   type="add" dev="ggregory" due-to="Gary Gregory">Add FutureTasks.</action>
+    <action                   type="add" dev="ggregory" due-to="Gary Gregory">Add Memoizer(Function) and Memoizer(Function, boolean).</action>
     <!-- UPDATE -->
     <action                   type="update" dev="ggregory" due-to="Dependabot, Gary Gregory">Bump spotbugs-maven-plugin from 4.2.0 to 4.5.0.0 #735, #808, #822, #834.</action>
     <action                   type="update" dev="ggregory" due-to="Dependabot, XenoAmess">Bump actions/cache from v2.1.4 to v2.1.7 #742, #752, #764, #833.</action>

src/main/java/org/apache/commons/lang3/concurrent/Memoizer.java

@@ -55,7 +55,7 @@ public class Memoizer<I, O> implements Computable<I, O> {
      * Constructs a Memoizer for the provided Computable calculation.
      * </p>
      * <p>
-     * If a calculation is thrown an exception for any reason, this exception will be cached and returned for all future
+     * If a calculation throws an exception for any reason, this exception will be cached and returned for all future
      * calls with the provided parameter.
      * </p>
      *
@@ -80,6 +80,38 @@ public class Memoizer<I, O> implements Computable<I, O> {
         this.mappingFunction = k -> FutureTasks.run(() -> computable.compute(k));
     }
 
+    /**
+     * <p>
+     * Constructs a Memoizer for the provided Function calculation.
+     * </p>
+     * <p>
+     * If a calculation throws an exception for any reason, this exception will be cached and returned for all future
+     * calls with the provided parameter.
+     * </p>
+     *
+     * @param function the function whose results should be memorized
+     * @since 2.13.0
+     */
+    public Memoizer(final Function<I, O> function) {
+        this(function, false);
+    }
+
+    /**
+     * <p>
+     * Constructs a Memoizer for the provided Function calculation, with the option of whether a Function that
+     * experiences an error should recalculate on subsequent calls or return the same cached exception.
+     * </p>
+     *
+     * @param function the computation whose results should be memorized
+     * @param recalculate determines whether the computation should be recalculated on subsequent calls if the previous call
+     *        failed
+     * @since 2.13.0
+     */
+     public Memoizer(final Function<I, O> function, final boolean recalculate) {
+        this.recalculate = recalculate;
+        this.mappingFunction = k -> FutureTasks.run(() -> function.apply(k));
+    }
+
     /**
      * <p>
      * This method will return the result of the calculation and cache it, if it has not previously been calculated.

src/test/java/org/apache/commons/lang3/concurrent/MemoizerComputableTest.java

@@ -25,7 +25,7 @@ import org.easymock.EasyMock;
 import org.junit.jupiter.api.BeforeEach;
 import org.junit.jupiter.api.Test;
 
-public class MemoizerTest {
+public class MemoizerComputableTest {
 
     private Computable<Integer, Integer> computable;
 
@@ -34,17 +34,6 @@ public class MemoizerTest {
         computable = EasyMock.mock(Computable.class);
     }
 
-    @Test
-    public void testOnlyCallComputableOnceIfDoesNotThrowException() throws Exception {
-        final Integer input = 1;
-        final Memoizer<Integer, Integer> memoizer = new Memoizer<>(computable);
-        expect(computable.compute(input)).andReturn(input);
-        replay(computable);
-
-        assertEquals(input, memoizer.compute(input), "Should call computable first time");
-        assertEquals(input, memoizer.compute(input), "Should not call the computable the second time");
-    }
-
     @Test
     public void testDefaultBehaviourNotToRecalculateExecutionExceptions() throws Exception {
         final Integer input = 1;
@@ -83,14 +72,14 @@ public class MemoizerTest {
     }
 
     @Test
-    public void testWhenComputableThrowsRuntimeException() throws Exception {
+    public void testOnlyCallComputableOnceIfDoesNotThrowException() throws Exception {
         final Integer input = 1;
         final Memoizer<Integer, Integer> memoizer = new Memoizer<>(computable);
-        final RuntimeException runtimeException = new RuntimeException("Some runtime exception");
-        expect(computable.compute(input)).andThrow(runtimeException);
+        expect(computable.compute(input)).andReturn(input);
         replay(computable);
 
-        assertThrows(RuntimeException.class, () -> memoizer.compute(input));
+        assertEquals(input, memoizer.compute(input), "Should call computable first time");
+        assertEquals(input, memoizer.compute(input), "Should not call the computable the second time");
     }
 
     @Test
@@ -103,4 +92,15 @@ public class MemoizerTest {
 
         assertThrows(Error.class, () -> memoizer.compute(input));
     }
+
+    @Test
+    public void testWhenComputableThrowsRuntimeException() throws Exception {
+        final Integer input = 1;
+        final Memoizer<Integer, Integer> memoizer = new Memoizer<>(computable);
+        final RuntimeException runtimeException = new RuntimeException("Some runtime exception");
+        expect(computable.compute(input)).andThrow(runtimeException);
+        replay(computable);
+
+        assertThrows(RuntimeException.class, () -> memoizer.compute(input));
+    }
 }

src/test/java/org/apache/commons/lang3/concurrent/MemoizerFunctionTest.java

@@ -0,0 +1,108 @@
+/*
+ * 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.concurrent;
+
+import static org.easymock.EasyMock.expect;
+import static org.easymock.EasyMock.replay;
+import static org.junit.jupiter.api.Assertions.assertEquals;
+import static org.junit.jupiter.api.Assertions.assertThrows;
+
+import java.util.function.Function;
+
+import org.easymock.EasyMock;
+import org.junit.jupiter.api.BeforeEach;
+import org.junit.jupiter.api.Test;
+
+public class MemoizerFunctionTest {
+
+    private Function<Integer, Integer> function;
+
+    @BeforeEach
+    public void setUpComputableMock() {
+        function = EasyMock.mock(Function.class);
+    }
+
+    @Test
+    public void testDefaultBehaviourNotToRecalculateExecutionExceptions() throws Exception {
+        final Integer input = 1;
+        final Memoizer<Integer, Integer> memoizer = new Memoizer<>(function);
+        final IllegalArgumentException interruptedException = new IllegalArgumentException();
+        expect(function.apply(input)).andThrow(interruptedException);
+        replay(function);
+
+        assertThrows(Throwable.class, () -> memoizer.compute(input));
+        assertThrows(IllegalArgumentException.class, () -> memoizer.compute(input));
+    }
+
+    @Test
+    public void testDoesNotRecalculateWhenSetToFalse() throws Exception {
+        final Integer input = 1;
+        final Memoizer<Integer, Integer> memoizer = new Memoizer<>(function, false);
+        final IllegalArgumentException interruptedException = new IllegalArgumentException();
+        expect(function.apply(input)).andThrow(interruptedException);
+        replay(function);
+
+        assertThrows(Throwable.class, () -> memoizer.compute(input));
+        assertThrows(IllegalArgumentException.class, () -> memoizer.compute(input));
+    }
+
+    @Test
+    public void testDoesRecalculateWhenSetToTrue() throws Exception {
+        final Integer input = 1;
+        final Integer answer = 3;
+        final Memoizer<Integer, Integer> memoizer = new Memoizer<>(function, true);
+        final IllegalArgumentException interruptedException = new IllegalArgumentException();
+        expect(function.apply(input)).andThrow(interruptedException).andReturn(answer);
+        replay(function);
+
+        assertThrows(Throwable.class, () -> memoizer.compute(input));
+        assertEquals(answer, memoizer.compute(input));
+    }
+
+    @Test
+    public void testOnlyCallComputableOnceIfDoesNotThrowException() throws Exception {
+        final Integer input = 1;
+        final Memoizer<Integer, Integer> memoizer = new Memoizer<>(function);
+        expect(function.apply(input)).andReturn(input);
+        replay(function);
+
+        assertEquals(input, memoizer.compute(input), "Should call computable first time");
+        assertEquals(input, memoizer.compute(input), "Should not call the computable the second time");
+    }
+
+    @Test
+    public void testWhenComputableThrowsError() throws Exception {
+        final Integer input = 1;
+        final Memoizer<Integer, Integer> memoizer = new Memoizer<>(function);
+        final Error error = new Error();
+        expect(function.apply(input)).andThrow(error);
+        replay(function);
+
+        assertThrows(Error.class, () -> memoizer.compute(input));
+    }
+
+    @Test
+    public void testWhenComputableThrowsRuntimeException() throws Exception {
+        final Integer input = 1;
+        final Memoizer<Integer, Integer> memoizer = new Memoizer<>(function);
+        final RuntimeException runtimeException = new RuntimeException("Some runtime exception");
+        expect(function.apply(input)).andThrow(runtimeException);
+        replay(function);
+
+        assertThrows(RuntimeException.class, () -> memoizer.compute(input));
+    }
+}