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Hibernate example source code file (CollectionHelper.java)

This example Hibernate source code file (CollectionHelper.java) is included in the DevDaily.com "Java Source Code Warehouse" project. The intent of this project is to help you "Learn Java by Example" TM.

Java - Hibernate tags/keywords

arraylist, arraylist, collectionhelper, concurrenthashmap, concurrenthashmap, hashmap, k,v, k,v, list, load_factor, load_factor, map, minimum_initial_capacity, t, threading, threads, util

The Hibernate CollectionHelper.java source code

/*
 * Hibernate, Relational Persistence for Idiomatic Java
 *
 * Copyright (c) 2008, Red Hat Middleware LLC or third-party contributors as
 * indicated by the @author tags or express copyright attribution
 * statements applied by the authors.  All third-party contributions are
 * distributed under license by Red Hat Middleware LLC.
 *
 * This copyrighted material is made available to anyone wishing to use, modify,
 * copy, or redistribute it subject to the terms and conditions of the GNU
 * Lesser General Public License, as published by the Free Software Foundation.
 *
 * 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 Lesser General Public License
 * for more details.
 *
 * You should have received a copy of the GNU Lesser General Public License
 * along with this distribution; if not, write to:
 * Free Software Foundation, Inc.
 * 51 Franklin Street, Fifth Floor
 * Boston, MA  02110-1301  USA
 */
package org.hibernate.internal.util.collections;

import java.util.ArrayList;
import java.util.Collection;
import java.util.Collections;
import java.util.HashMap;
import java.util.List;
import java.util.Map;
import java.util.Set;
import java.util.concurrent.ConcurrentHashMap;

/**
 * Various help for handling collections.
 *
 * @author Gavin King
 * @author Steve Ebersole
 */
public final class CollectionHelper {
    public static final int MINIMUM_INITIAL_CAPACITY = 16;
	public static final float LOAD_FACTOR = 0.75f;

	public static final List EMPTY_LIST = Collections.unmodifiableList( new ArrayList(0) );
	public static final Collection EMPTY_COLLECTION = Collections.unmodifiableCollection( new ArrayList(0) );
	public static final Map EMPTY_MAP = Collections.unmodifiableMap( new HashMap(0) );

	private CollectionHelper() {
	}

	/**
	 * Build a properly sized map, especially handling load size and load factor to prevent immediate resizing.
	 * <p/>
	 * Especially helpful for copy map contents.
	 *
	 * @param size The size to make the map.
	 * @return The sized map.
	 */
	public static <K,V> Map mapOfSize(int size) {
		return new HashMap<K,V>( determineProperSizing( size ), LOAD_FACTOR );
	}

	/**
	 * Given a map, determine the proper initial size for a new Map to hold the same number of values.
	 * Specifically we want to account for load size and load factor to prevent immediate resizing.
	 *
	 * @param original The original map
	 * @return The proper size.
	 */
	public static int determineProperSizing(Map original) {
		return determineProperSizing( original.size() );
	}

	/**
	 * Given a set, determine the proper initial size for a new set to hold the same number of values.
	 * Specifically we want to account for load size and load factor to prevent immediate resizing.
	 *
	 * @param original The original set
	 * @return The proper size.
	 */
	public static int determineProperSizing(Set original) {
		return determineProperSizing( original.size() );
	}

	/**
	 * Determine the proper initial size for a new collection in order for it to hold the given a number of elements.
	 * Specifically we want to account for load size and load factor to prevent immediate resizing.
	 *
	 * @param numberOfElements The number of elements to be stored.
	 * @return The proper size.
	 */
	public static int determineProperSizing(int numberOfElements) {
		int actual = ( (int) (numberOfElements / LOAD_FACTOR) ) + 1;
		return Math.max( actual, MINIMUM_INITIAL_CAPACITY );
	}

	/**
	 * Create a properly sized {@link ConcurrentHashMap} based on the given expected number of elements.
	 *
	 * @param expectedNumberOfElements The expected number of elements for the created map
	 * @param <K> The map key type
	 * @param <V> The map value type
	 *
	 * @return The created map.
	 */
	public static <K,V> ConcurrentHashMap concurrentMap(int expectedNumberOfElements) {
		return concurrentMap( expectedNumberOfElements, LOAD_FACTOR );
	}

	/**
	 * Create a properly sized {@link ConcurrentHashMap} based on the given expected number of elements and an
	 * explicit load factor
	 *
	 * @param expectedNumberOfElements The expected number of elements for the created map
	 * @param loadFactor The collection load factor
	 * @param <K> The map key type
	 * @param <V> The map value type
	 *
	 * @return The created map.
	 */
	public static <K,V> ConcurrentHashMap concurrentMap(int expectedNumberOfElements, float loadFactor) {
		final int size = expectedNumberOfElements + 1 + (int) ( expectedNumberOfElements * loadFactor );
		return new ConcurrentHashMap<K, V>( size, loadFactor );
	}

	public static <T> List arrayList(int anticipatedSize) {
		return new ArrayList<T>( anticipatedSize );
	}

    public static boolean isEmpty(Collection collection) {
        return collection == null || collection.isEmpty();
    }

    public static boolean isEmpty(Map map) {
        return map == null || map.isEmpty();
    }

    public static boolean isNotEmpty(Collection collection) {
        return !isEmpty( collection );
    }

    public static boolean isNotEmpty(Map map) {
        return !isEmpty( map );
    }
}

Other Hibernate examples (source code examples)

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