org.openmdx.base.collection.Maps Maven / Gradle / Ivy
/*
* ====================================================================
* Project: openMDX, http://www.openmdx.org/
* Description: Maps
* Owner: OMEX AG, Switzerland, http://www.omex.ch
* ====================================================================
*
* This software is published under the BSD license as listed below.
*
* Copyright (c) 2008,-2017 OMEX AG, Switzerland
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or
* without modification, are permitted provided that the following
* conditions are met:
*
* * Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
*
* * Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in
* the documentation and/or other materials provided with the
* distribution.
*
* * Neither the name of the openMDX team nor the names of its
* contributors may be used to endorse or promote products derived
* from this software without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND
* CONTRIBUTORS "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES,
* INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF
* MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
* DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS
* BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
* EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED
* TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
* DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON
* ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
* OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
* POSSIBILITY OF SUCH DAMAGE.
*
* ------------------
*
* This product includes software developed by other organizations as
* listed in the NOTICE file.
*/
package org.openmdx.base.collection;
import java.util.HashMap;
import java.util.Map;
import java.util.concurrent.ConcurrentHashMap;
/**
* Maps
*/
public class Maps {
/**
* Constructor
*/
protected Maps() {
// Avoid instantiation
}
/**
* A NULL value for maps not allowing null as value.
*/
public static final Object NULL = new Object();
/**
* Create a null masking hash map
*
* @param threadSafetyRequired
* defines whether thread safety is required or not
*
* @return a newly created null masking map
*/
@SuppressWarnings("unchecked")
public static Map newMapSupportingNullValues(
boolean threadSafetyRequired
){
return threadSafetyRequired ? NullMaskingMap.decorate(
new ConcurrentHashMap(),
NULL
) : new HashMap<>();
}
/**
* Create a concurrent or standard hash map, depending on the argument.
* {@code null} will neither be supported as key nor as value
*
* @param threadSafetyRequired
* defines whether thread safety is required or not
*
* @return a newly created hash map
*/
public static Map newMap(
boolean threadSafetyRequired
){
return threadSafetyRequired ? new ConcurrentHashMap<>() : new HashMap<>();
}
/**
* Return the actual value
*
* @param target the concurrent map
* @param key
* @param value
*
* @return the new or kept value
*/
public static V putUnlessPresent(
Map target,
K key,
V value
){
V concurrent = target.putIfAbsent(key, value);
return concurrent == null ? value : concurrent;
}
}