Memoize.java
/*
* *********************************************************************************************************************
*
* blueMarine II: Semantic Media Centre
* http://tidalwave.it/projects/bluemarine2
*
* Copyright (C) 2015 - 2021 by Tidalwave s.a.s. (http://tidalwave.it)
*
* *********************************************************************************************************************
*
* 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.
*
* *********************************************************************************************************************
*
* git clone https://bitbucket.org/tidalwave/bluemarine2-src
* git clone https://github.com/tidalwave-it/bluemarine2-src
*
* *********************************************************************************************************************
*/
package it.tidalwave.util;
import javax.annotation.Nonnull;
import java.util.function.Supplier;
import static java.util.Objects.requireNonNull;
/***********************************************************************************************************************
*
* @author Fabrizio Giudici
*
**********************************************************************************************************************/
public class Memoize<T>
{
private T value;
private transient volatile boolean initialized;
private transient volatile Supplier<T> supplier;
public Memoize()
{
}
public Memoize (@Nonnull final Supplier<T> supplier)
{
this.supplier = supplier;
}
@Nonnull
public T get()
{
return get(requireNonNull(supplier, "get() can be used if the Supplier has been provided in the constructor"));
}
@Nonnull
public T get (@Nonnull final Supplier<T> supplier)
{
if (!initialized) // double checked locking
{
synchronized (this)
{
if (!initialized)
{
value = supplier.get();
initialized = true;
}
}
}
return value;
}
}