org.neo4j.kernel.impl.util.InstanceCache Maven / Gradle / Ivy

Go to download

Show more of this group Show more artifacts with this name
Show all versions of neo4j-kernel Show documentation

Neo4j kernel is a lightweight, embedded Java database designed to store data structured as graphs rather than tables. For more information, see http://neo4j.org.

There is a newer version: 5.26.1

Show newest version

/*
 * Copyright (c) 2002-2016 "Neo Technology,"
 * Network Engine for Objects in Lund AB [http://neotechnology.com]
 *
 * This file is part of Neo4j.
 *
 * Neo4j is free software: you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation, either version 3 of the License, or
 * (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program.  If not, see .
 */
package org.neo4j.kernel.impl.util;

import java.util.function.Consumer;
import java.util.function.Supplier;

/**
 * Caches single instances. This is meant to be used within a single thread, where
 * the usage pattern is such that it is likely that at any given time only one T is needed, but at times
 * more than one T is used. This cache will for the majority of cases cache that single instance.
 *
 * @param 
 */
public abstract class InstanceCache implements Supplier, Consumer
{
    private T instance;

    @Override
    public T get()
    {
        if ( instance == null )
        {
            instance = create();
        }

        try
        {
            return instance;
        }
        finally
        {
            instance = null;
        }
    }

    @Override
    public void accept( T instance )
    {
        this.instance = instance;
    }

    protected abstract T create();
}