001/*
002 * ============================================================================
003 * Copyright © 2002-2021 by Thomas Thrien.
004 * All Rights Reserved.
005 * ============================================================================
006 * Licensed to the public under the agreements of the GNU Lesser General Public
007 * License, version 3.0 (the "License"). You may obtain a copy of the License at
008 *
009 *      http://www.gnu.org/licenses/lgpl.html
010 *
011 * Unless required by applicable law or agreed to in writing, software
012 * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
013 * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
014 * License for the specific language governing permissions and limitations
015 * under the License.
016 */
017
018package org.tquadrat.foundation.lang.internal;
019
020import static org.apiguardian.api.API.Status.INTERNAL;
021import static org.tquadrat.foundation.lang.Objects.isNull;
022import static org.tquadrat.foundation.lang.Objects.requireNonNullArgument;
023
024import java.lang.ref.SoftReference;
025import java.util.Optional;
026import java.util.function.Supplier;
027
028import org.apiguardian.api.API;
029import org.tquadrat.foundation.annotation.ClassVersion;
030import org.tquadrat.foundation.lang.SoftLazy;
031
032/**
033 *  The implementation for the
034 *  {@link SoftLazy}
035 *  interface.
036 *
037 *  @extauthor Thomas Thrien - thomas.thrien@tquadrat.org
038 *  @version $Id: SoftLazyImpl.java 1031 2022-04-07 22:43:02Z tquadrat $
039 *  @since 0.1.0
040 *
041 *  @param  <T> The type of the cached data.
042 */
043@API( status = INTERNAL, since = "0.1.0" )
044@ClassVersion( sourceVersion = "$Id: SoftLazyImpl.java 1031 2022-04-07 22:43:02Z tquadrat $" )
045public final class SoftLazyImpl<T> implements SoftLazy<T>
046{
047        /*-----------*\
048    ====** Constants **========================================================
049        \*-----------*/
050    /**
051     *  An empty array of {@code SoftLazyImpl<T>} objects.
052     */
053    @SuppressWarnings( "rawtypes" )
054    public static final SoftLazyImpl [] EMPTY_SoftLazyImpl_ARRAY = new SoftLazyImpl [0];
055
056        /*------------*\
057    ====** Attributes **=======================================================
058        \*------------*/
059    /**
060     *  The initializer method.
061     */
062    private final Supplier<T> m_Initializer;
063
064    /**
065     *  The data reference.
066     */
067    @SuppressWarnings( "OptionalUsedAsFieldOrParameterType" )
068    private Optional<SoftReference<T>> m_Reference = Optional.empty();
069
070        /*--------------*\
071    ====** Constructors **=====================================================
072        \*--------------*/
073    /**
074     *  Creates a new {@code SoftLazyImpl<T>} instance.
075     *
076     *  @param  initializer The initializer method.
077     */
078    public SoftLazyImpl( final Supplier<T> initializer )
079    {
080        m_Initializer = requireNonNullArgument( initializer, "initializer" );
081    }   //  SoftLazyImpl<T>()
082
083        /*---------*\
084    ====** Methods **==========================================================
085        \*---------*/
086    /**
087     *  Creates the reference to the data.
088     *
089     *  @return The reference.
090     */
091    private final SoftReference<T> createReference()
092    {
093        final var data = m_Initializer.get();
094        final var retValue = new SoftReference<>( data );
095
096        //---* Done *----------------------------------------------------------
097        return retValue;
098    }   //  createReference()
099
100    /**
101     *  {@inheritDoc}
102     */
103    @Override
104    public final T get()
105    {
106        var updateReference = m_Reference.isEmpty();
107        var reference = m_Reference.orElseGet( this::createReference );
108        var retValue = reference.get();
109        if( isNull( retValue ) )
110        {
111            updateReference = true;
112            reference = createReference();
113            retValue = reference.get();
114        }
115        if( updateReference ) m_Reference = Optional.of( reference );
116
117        //---* Done *----------------------------------------------------------
118        return retValue;
119    }   //  get()
120}
121//  class SoftLazyImpl
122
123/*
124 *  End of File
125 */