org.apache.mina.util.LazyInitializer Maven / Gradle / Ivy

/**
 * Copyright 2007-2015, Kaazing Corporation. All rights reserved.
 *
 * Licensed 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.mina.util;

/**
 * An abstract class which provides semantics for an object which will be only
 * fully initialized when requested to. It allows to avoid loosing time when 
 * early initializing unnecessary objects.
 * 
 * @author Apache MINA Project
 * @since MINA 2.0.0-M2
 */
public abstract class LazyInitializer {

    /**
     * The value that results on the {@link #init()} call. If null,
     * it means that the value has not been initialized yet.
     */
    private V value;

    /**
     * Initializes the value.
     *
     * @return the initialized value
     */
    public abstract V init();

    /**
     * Returns the value resulting from the initialization.
     * @return the initialized value
     */
    public V get() {
        if (value == null) {
            value = init();
        }

        return value;
    }
}