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/*
* Copyright (c) 2011, 2019 Oracle and/or its affiliates. All rights reserved.
*
* This program and the accompanying materials are made available under the
* terms of the Eclipse Public License v. 2.0, which is available at
* http://www.eclipse.org/legal/epl-2.0.
*
* This Source Code may also be made available under the following Secondary
* Licenses when the conditions for such availability set forth in the
* Eclipse Public License v. 2.0 are satisfied: GNU General Public License,
* version 2 with the GNU Classpath Exception, which is available at
* https://www.gnu.org/software/classpath/license.html.
*
* SPDX-License-Identifier: EPL-2.0 OR GPL-2.0 WITH Classpath-exception-2.0
*/
package org.glassfish.jersey.internal.util.collection;
import java.util.Map;
import java.util.concurrent.BlockingQueue;
import java.util.concurrent.ConcurrentHashMap;
import java.util.concurrent.ConcurrentMap;
import java.util.concurrent.LinkedTransferQueue;
/**
* Utility class, which tries to pickup the best collection implementation depending
* on running environment.
*
* @author Gustav Trede
* @author Marek Potociar
* @since 2.3
*/
public final class DataStructures {
/**
* Default concurrency level calculated based on the number of available CPUs.
*/
public static final int DEFAULT_CONCURENCY_LEVEL = ceilingNextPowerOfTwo(Runtime.getRuntime().availableProcessors());
private static int ceilingNextPowerOfTwo(final int x) {
// Hacker's Delight, Chapter 3, Harry S. Warren Jr.
return 1 << (Integer.SIZE - Integer.numberOfLeadingZeros(x - 1));
}
/**
* Create an instance of a {@link BlockingQueue} that is based on
* {@code LinkedTransferQueue} implementation, available in JDK 7 and above.
*
* Originally, the method was used to provide backwards compatibility for JDK versions 6 and below.
* As those versions are now unsupported, callers should instantiate an {@link LinkedTransferQueue}
* directly instead of using this method.
*
*
* @param the type of elements held in the queue.
* @return new instance of a {@link BlockingQueue} that is based on {@code LinkedTransferQueue}
* implementation from JDK 7.
*/
@Deprecated
public static BlockingQueue createLinkedTransferQueue() {
return new LinkedTransferQueue<>();
}
/**
* Creates a new, empty map with a default initial capacity (16),
* load factor (0.75) and concurrencyLevel (16).
*
* The method was originally used to provide the
*
* {@code ConcurrentHashMapV8}, available in JDK 8 and above, for JDK 7 or earlier.
* As those versions are now unsupported, callers should instantiate an {@link ConcurrentHashMap}
* directly instead of using this method.
*
*
* @return the map.
*/
@Deprecated
public static ConcurrentMap createConcurrentMap() {
return new ConcurrentHashMap<>();
}
/**
* Creates a new map with the same mappings as the given map.
*
* The method was originally used to provide the
*
* {@code ConcurrentHashMapV8}, available in JDK 8 and above, for JDK 7 or earlier.
* As those versions are now unsupported, callers should instantiate an {@link ConcurrentHashMap}
* directly instead of using this method.
*
*
* @param map the map.
*/
@Deprecated
public static ConcurrentMap createConcurrentMap(
final Map map) {
return new ConcurrentHashMap<>(map);
}
/**
* Creates a new, empty map with an initial table size accommodating the specified
* number of elements without the need to dynamically resize.
*
* The method was originally used to provide the
*
* {@code ConcurrentHashMapV8}, available in JDK 8 and above, for JDK 7 or earlier.
* As those versions are now unsupported, callers should instantiate an {@link ConcurrentHashMap}
* directly instead of using this method.
*
*
* @param initialCapacity The implementation performs internal
* sizing to accommodate this many elements.
* @throws IllegalArgumentException if the initial capacity of
* elements is negative.
*/
@Deprecated
public static ConcurrentMap createConcurrentMap(
final int initialCapacity) {
return new ConcurrentHashMap<>(initialCapacity);
}
/**
* Creates a new, empty map with an initial table size based on the given number of elements
* ({@code initialCapacity}), table density ({@code loadFactor}), and number of concurrently
* updating threads ({@code concurrencyLevel}).
*
* The method was originally used to provide the
*
* {@code ConcurrentHashMapV8}, available in JDK 8 and above, for JDK 7 or earlier.
* As those versions are now unsupported, callers should instantiate an {@link ConcurrentHashMap}
* directly instead of using this method.
*
*
* @param initialCapacity the initial capacity. The implementation
* performs internal sizing to accommodate this many elements,
* given the specified load factor.
* @param loadFactor the load factor (table density) for
* establishing the initial table size.
* @param concurrencyLevel the estimated number of concurrently
* updating threads. The implementation may use this value as
* a sizing hint.
* @throws IllegalArgumentException if the initial capacity is
* negative or the load factor or concurrencyLevel are
* not positive.
*/
@Deprecated
public static ConcurrentMap createConcurrentMap(
final int initialCapacity, final float loadFactor,
final int concurrencyLevel) {
return new ConcurrentHashMap<>(initialCapacity, loadFactor, concurrencyLevel);
}
}