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Java utility collections, development by Nervousync Studio (NSYC)

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/*
 * Licensed to the Nervousync Studio (NSYC) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You under the Apache License, Version 2.0
 * (the "License"); you may not use this file except in compliance with
 * the License.  You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package org.nervousync.utils;

import java.util.ArrayList;
import java.util.Arrays;
import java.util.Collection;
import java.util.Collections;
import java.util.Enumeration;
import java.util.Iterator;
import java.util.List;
import java.util.Map;
import java.util.Properties;

/**
 * @author Steven Wee	[email protected]
 * @version $Revision: 1.0 $ $Date: Jan 13, 2010 4:27:49 PM $
 */
public final class CollectionUtils {
	
	private CollectionUtils() {
	}

	/**
	 * Sort number collection
	 * @param collection	collection
	 * @return				Sorted collection
	 */
	public static List sort(Collection collection) {
		List returnList = new ArrayList<>(collection);
		Collections.sort(returnList);
		return returnList;
	}

	/**
	 * Sort number collection and reverse result
	 * @param collection	collection
	 * @return				Sorted and reverse collection
	 */
	public static List sortAndReverse(Collection collection) {
		List returnList = new ArrayList<>(collection);
		Collections.sort(returnList);
		Collections.reverse(returnList);
		return returnList;
	}
	
	/**
	 * Return true if the supplied Collection is null
	 * or empty. Otherwise, return false.
	 * @param collection the Collection to check
	 * @return whether the given Collection is empty
	 */
	public static boolean isEmpty(Collection collection) {
		return (collection == null || collection.isEmpty());
	}

	/**
	 * Return true if the supplied Map is null
	 * or empty. Otherwise, return false.
	 * @param map the Map to check
	 * @return whether the given Map is empty
	 */
	public static boolean isEmpty(Map map) {
		return (map == null || map.isEmpty());
	}

	/**
	 * Convert the supplied array into a List. A primitive array gets
	 * converted into a List of the appropriate wrapper type.
	 * 
A null source value will be converted to an
	 * empty List.
	 * @param source the (potentially primitive) array
	 * @return the converted List result
	 * @see ObjectUtils#toObjectArray(Object)
	 */
	public static List arrayToList(Object source) {
		return Arrays.asList(ObjectUtils.toObjectArray(source));
	}

	/**
	 * Convert arrays to list
	 * @param a		arrays
	 * @param 	T
	 * @return		Convert list
	 */
	public static  List asList(T[] a) {
		return Arrays.asList(a);
	}

	/**
	 * Merge the given array into the given Collection.
	 * @param array the array to merge (maybe null)
	 * @param collection the target Collection to merge the array into
	 */
	public static void mergeArrayIntoCollection(Object array, Collection collection) {
		if (collection == null) {
			throw new IllegalArgumentException("Collection must not be null");
		}
		Object[] arr = ObjectUtils.toObjectArray(array);
		Collections.addAll(collection, arr);
	}

	/**
	 * Merge the given Properties instance into the given Map,
	 * copying all properties (key-value pairs) over.
	 * 
Uses Properties.propertyNames() to even catch
	 * default properties linked into the original Properties instance.
	 * @param props the Properties instance to merge (maybe null)
	 * @param map the target Map to merge the properties into
	 */
	public static void mergePropertiesIntoMap(Properties props, Map map) {
		if (map == null) {
			throw new IllegalArgumentException("Map must not be null");
		}
		if (props != null) {
			for (Enumeration en = props.propertyNames(); en.hasMoreElements();) {
				String key = (String) en.nextElement();
				map.put(key, props.getProperty(key));
			}
		}
	}


	/**
	 * Check whether the given Iterator contains the given element.
	 * @param iterator the Iterator to check
	 * @param element the element to look for
	 * @return true if found, false else
	 */
	public static boolean contains(Iterator iterator, Object element) {
		if (iterator != null) {
			while (iterator.hasNext()) {
				Object candidate = iterator.next();
				if (ObjectUtils.nullSafeEquals(candidate, element)) {
					return true;
				}
			}
		}
		return false;
	}

	/**
	 * Check whether the given Enumeration contains the given element.
	 * @param enumeration the Enumeration to check
	 * @param element the element to look for
	 * @return true if found, false else
	 */
	public static boolean contains(Enumeration enumeration, Object element) {
		if (enumeration != null) {
			while (enumeration.hasMoreElements()) {
				Object candidate = enumeration.nextElement();
				if (ObjectUtils.nullSafeEquals(candidate, element)) {
					return true;
				}
			}
		}
		return false;
	}

	/**
	 * Check whether the given Collection contains the given element instance.
	 * 
Enforces the given instance to be present, rather than returning
	 * true for an equal element as well.
	 * @param collection the Collection to check
	 * @param element the element to look for
	 * @return true if found, false else
	 */
	public static boolean containsInstance(Collection collection, Object element) {
		if (collection != null) {
			for (Object candidate : collection) {
				if (candidate == element) {
					return true;
				}
			}
		}
		return false;
	}

	/**
	 * Return true if any element in 'candidates' is
	 * contained in 'source'; otherwise returns false.
	 * @param source the source Collection
	 * @param candidates the candidates to search for
	 * @return whether any of the candidates has been found
	 */
	public static boolean containsAny(Collection source, Collection candidates) {
		if (isEmpty(source) || isEmpty(candidates)) {
			return false;
		}
		for (Object candidate : candidates) {
			if (source.contains(candidate)) {
				return true;
			}
		}
		return false;
	}

	/**
	 * Return the first element in 'candidates' that is contained in
	 * 'source'. If no element in 'candidates' is present in
	 * 'source' returns null. Iteration order is
	 * {@link Collection} implementation specific.
	 * @param source the source Collection
	 * @param candidates the candidates to search for
	 * @return the first present object, or null if not found
	 */
	public static Object findFirstMatch(Collection source, Collection candidates) {
		if (isEmpty(source) || isEmpty(candidates)) {
			return null;
		}
		for (Object candidate : candidates) {
			if (source.contains(candidate)) {
				return candidate;
			}
		}
		return null;
	}

	/**
	 * Find a single value of the given type in the given Collection.
	 * @param collection the Collection to search
	 * @param type the type to look for
	 * @return a value of the given type found if there is a clear match,
	 * or null if none or more than one such value found
	 */
	public static Object findValueOfType(Collection collection, Class type) {
		if (isEmpty(collection)) {
			return null;
		}
		Object value = null;
		for (Object obj : collection) {
			if (type == null || type.isInstance(obj)) {
				if (value != null) {
					// More than one value found... no clear single value.
					return null;
				}
				value = obj;
			}
		}
		return value;
	}

	/**
	 * Find a single value of one of the given types in the given Collection:
	 * searching the Collection for a value of the first type, then
	 * searching for a value of the second type, etc.
	 * @param collection the collection to search
	 * @param types the types to look for, in prioritized order
	 * @return a value of one of the given types found if there is a clear match,
	 * or null if none or more than one such value found
	 */
	public static Object findValueOfType(Collection collection, Class[] types) {
		if (isEmpty(collection) || ObjectUtils.isEmpty(types)) {
			return null;
		}
		for (Class type : types) {
			Object value = findValueOfType(collection, type);
			if (value != null) {
				return value;
			}
		}
		return null;
	}

	/**
	 * Determine whether the given Collection only contains a single unique object.
	 * @param collection the Collection to check
	 * @return true if the collection contains a single reference or
	 * multiple references to the same instance, false else
	 */
	public static boolean hasUniqueObject(Collection collection) {
		if (isEmpty(collection)) {
			return false;
		}
		boolean hasCandidate = false;
		Object candidate = null;
		for (Object elem : collection) {
			if (!hasCandidate) {
				hasCandidate = true;
				candidate = elem;
			} else if (candidate != elem) {
				return false;
			}
		}
		return true;
	}
}
    

    

    

            

    

            



    
    






    
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