CollectionUtil.java

package javaToolkit.lib.utils;

import java.util.*;

public class CollectionUtil {

	/**
	 * https://stackoverflow.com/a/109389/4315608
	 *
	 * @param map
	 * @param <K>
	 * @param <V>
	 * @return
	 */
	public static <K, V> Map<K, V> sortByValue(Map<K, V> map) {
		List<Map.Entry<K, V>> list = new LinkedList<>(map.entrySet());
		Collections.sort(list, new Comparator<Object>() {
			@SuppressWarnings("unchecked")
			public int compare(Object o1, Object o2) {
				return ((Comparable<V>) ((Map.Entry<K, V>) (o1)).getValue())
						.compareTo(((Map.Entry<K, V>) (o2)).getValue());
			}
		});

		Map<K, V> result = new LinkedHashMap<>();
		for (Iterator<Map.Entry<K, V>> it = list.iterator(); it.hasNext();) {
			Map.Entry<K, V> entry = (Map.Entry<K, V>) it.next();
			result.put(entry.getKey(), entry.getValue());
		}

		return result;
	}

	public static Set<Object> mergeMultipleSet(List<Set<Object>> multiSet) {
		Set<Object> mergeSet = new HashSet<>();
		for (Set<Object> set : multiSet) {
			mergeSet.addAll(set);
		}
		return mergeSet;
	}

}