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/*
* Hibernate, Relational Persistence for Idiomatic Java
*
* License: GNU Lesser General Public License (LGPL), version 2.1 or later.
* See the lgpl.txt file in the root directory or .
*/
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.HashSet;
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;
/**
* @deprecated use {@link java.util.Collections#EMPTY_LIST} or {@link java.util.Collections#emptyList()} instead
*/
@Deprecated
public static final List EMPTY_LIST = Collections.EMPTY_LIST;
/**
* @deprecated use {@link java.util.Collections#EMPTY_LIST} or {@link java.util.Collections#emptyList()} instead
*/
@Deprecated
public static final Collection EMPTY_COLLECTION = Collections.EMPTY_LIST;
/**
* @deprecated use {@link java.util.Collections#EMPTY_MAP} or {@link java.util.Collections#emptyMap()} instead
*/
@Deprecated
public static final Map EMPTY_MAP = Collections.EMPTY_MAP;
private CollectionHelper() {
}
/**
* Build a properly sized map, especially handling load size and load factor to prevent immediate resizing.
*
* Especially helpful for copy map contents.
*
* @param size The size to make the map.
*
* @return The sized map.
*/
public static Map mapOfSize(int size) {
return new HashMap( 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 The map key type
* @param The map value type
*
* @return The created map.
*/
public static 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 The map key type
* @param The map value type
*
* @return The created map.
*/
public static ConcurrentHashMap concurrentMap(int expectedNumberOfElements, float loadFactor) {
final int size = expectedNumberOfElements + 1 + (int) ( expectedNumberOfElements * loadFactor );
return new ConcurrentHashMap( size, loadFactor );
}
public static ArrayList arrayList(int anticipatedSize) {
return new ArrayList( anticipatedSize );
}
public static Set makeCopy(Set source) {
if ( source == null ) {
return null;
}
final int size = source.size();
final Set copy = new HashSet( size + 1 );
copy.addAll( source );
return copy;
}
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 );
}
public static boolean isEmpty(Object[] objects) {
return objects == null || objects.length == 0;
}
public static Map makeCopy(Map map) {
final Map copy = mapOfSize( map.size() + 1 );
copy.putAll( map );
return copy;
}
}