src/main/java/org/apache/groovy/util/concurrent/LazyInitializable.java

/*
 *  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.groovy.util.concurrent;

/**
 *  A {@code LazyInitializable} is an object that can be initialized lazily.
 *  Note: the instance field {@code initialized} of sub-class should be {@code volatile} to avoid JVM instructions re-ordering
 *
 * @since 3.0.0
 */
public interface LazyInitializable {
    default void lazyInit() {
        if (isInitialized()) return;

        synchronized (this) {
            if (isInitialized()) return;
            doInit();
            setInitialized(true);
        }
    }

    /**
     * do initialization
     */
    void doInit();

    /**
     * Check if the object is initialized.
     *
     * @return the check result
     */
    boolean isInitialized();

    /**
     * Mark the object initialized.
     *
     * @param initialized initialized
     */
    void setInitialized(boolean initialized);
}