Refactor variable ConcurrentInitializer implementations to remove

duplication of initialize() method

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

@@ -0,0 +1,39 @@
+/*
+ * 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;
+
+/**
+ * Abstracts and defines operations for ConcurrentInitializer implementations.
+ *
+ * @param <T> the type of the object managed by this initializer class.
+ * @param <E> The exception type thrown by {@link #initialize()}.
+ * @since 3.14.0
+ */
+public abstract class AbstractConcurrentInitializer<T, E extends Exception> implements ConcurrentInitializer<T> {
+
+    /**
+     * Creates and initializes the object managed by this {@code
+     * ConcurrentInitializer}. This method is called by {@link #get()} when the object is accessed for the first time. An implementation can focus on the
+     * creation of the object. No synchronization is needed, as this is already handled by {@code get()}.
+     *
+     * @return the managed data object
+     * @throws E if an error occurs during object creation
+     */
+    protected abstract T initialize() throws E;
+
+}

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

@@ -62,7 +62,7 @@ import java.util.concurrent.atomic.AtomicReference;
  * @since 3.0
  * @param <T> the type of the object managed by this initializer class
  */
-public abstract class AtomicInitializer<T> implements ConcurrentInitializer<T> {
+public abstract class AtomicInitializer<T> extends AbstractConcurrentInitializer<T, RuntimeException> {
     /** Holds the reference to the managed object. */
     private final AtomicReference<T> reference = new AtomicReference<>();
 
@@ -89,17 +89,4 @@ public abstract class AtomicInitializer<T> implements ConcurrentInitializer<T> {
 
         return result;
     }
-
-    /**
-     * Creates and initializes the object managed by this {@code
-     * AtomicInitializer}. This method is called by {@link #get()} when the
-     * managed object is not available yet. An implementation can focus on the
-     * creation of the object. No synchronization is needed, as this is already
-     * handled by {@code get()}. As stated by the class comment, it is possible
-     * that this method is called multiple times.
-     *
-     * @return the managed data object
-     * @throws ConcurrentException if an error occurs during object creation
-     */
-    protected abstract T initialize() throws ConcurrentException;
 }

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

@@ -51,8 +51,8 @@ import java.util.concurrent.atomic.AtomicReference;
  * @since 3.0
  * @param <T> the type of the object managed by this initializer class
  */
-public abstract class AtomicSafeInitializer<T> implements
-        ConcurrentInitializer<T> {
+public abstract class AtomicSafeInitializer<T> extends AbstractConcurrentInitializer<T, RuntimeException> {
+
     /** A guard which ensures that initialize() is called only once. */
     private final AtomicReference<AtomicSafeInitializer<T>> factory =
             new AtomicReference<>();
@@ -79,17 +79,4 @@ public abstract class AtomicSafeInitializer<T> implements
 
         return result;
     }
-
-    /**
-     * Creates and initializes the object managed by this
-     * {@link AtomicInitializer}. This method is called by {@link #get()} when
-     * the managed object is not available yet. An implementation can focus on
-     * the creation of the object. No synchronization is needed, as this is
-     * already handled by {@code get()}. This method is guaranteed to be called
-     * only once.
-     *
-     * @return the managed data object
-     * @throws ConcurrentException if an error occurs during object creation
-     */
-    protected abstract T initialize() throws ConcurrentException;
 }

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

@@ -81,8 +81,8 @@ import java.util.concurrent.Future;
  * @since 3.0
  * @param <T> the type of the object managed by this initializer class
  */
-public abstract class BackgroundInitializer<T> implements
-        ConcurrentInitializer<T> {
+public abstract class BackgroundInitializer<T> extends AbstractConcurrentInitializer<T, Exception> {
+
     /** The external executor service for executing tasks. */
     private ExecutorService externalExecutor; // @GuardedBy("this")
 
@@ -262,18 +262,6 @@ public abstract class BackgroundInitializer<T> implements
         return 1;
     }
 
-    /**
-     * Performs the initialization. This method is called in a background task
-     * when this {@link BackgroundInitializer} is started. It must be
-     * implemented by a concrete subclass. An implementation is free to perform
-     * arbitrary initialization. The object returned by this method can be
-     * queried using the {@link #get()} method.
-     *
-     * @return a result object
-     * @throws Exception if an error occurs
-     */
-    protected abstract T initialize() throws Exception;
-
     /**
      * Creates a task for the background initialization. The {@link Callable}
      * object returned by this method is passed to the {@link ExecutorService}.

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

@@ -76,7 +76,7 @@ package org.apache.commons.lang3.concurrent;
  * @since 3.0
  * @param <T> the type of the object managed by this initializer class
  */
-public abstract class LazyInitializer<T> implements ConcurrentInitializer<T> {
+public abstract class LazyInitializer<T> extends AbstractConcurrentInitializer<T, ConcurrentException> {
 
     private static final Object NO_INIT = new Object();
 
@@ -110,18 +110,6 @@ public abstract class LazyInitializer<T> implements ConcurrentInitializer<T> {
         return result;
     }
 
-    /**
-     * Creates and initializes the object managed by this {@code
-     * LazyInitializer}. This method is called by {@link #get()} when the object
-     * is accessed for the first time. An implementation can focus on the
-     * creation of the object. No synchronization is needed, as this is already
-     * handled by {@code get()}.
-     *
-     * @return the managed data object
-     * @throws ConcurrentException if an error occurs during object creation
-     */
-    protected abstract T initialize() throws ConcurrentException;
-
     /**
      * Tests whether this instance is initialized. Once initialized, always returns true.
      *