MapHelpers.java

package tv.porst.splib.maps;

import java.util.Collections;
import java.util.Comparator;
import java.util.LinkedHashMap;
import java.util.LinkedList;
import java.util.List;
import java.util.Map;

/**
 * Contains helper functions for working with maps.
 */
public final class MapHelpers
{
  /**
   * Sorts a map by its values.
   *
   * @param <S>
   *          Type of map keys.
   * @param <T>
   *          Type of map values.
   * @param map
   *          The map to sort.
   *
   * @return The sorted map.
   */
  public static <S, T extends Comparable<T>> Map<S, T> sortByValue(final Map<S, T> map)
  {
    final List<Map.Entry<S, T>> list = new LinkedList<Map.Entry<S, T>>(map.entrySet());
    Collections.sort(list, new Comparator<Map.Entry<S, T>>() {
      @Override
      public int compare(final Map.Entry<S, T> o1, final Map.Entry<S, T> o2)
      {
        return o1.getValue().compareTo(o2.getValue());
      }
    });

    final Map<S, T> result = new LinkedHashMap<S, T>();
    for (final Map.Entry<S, T> element : list) {
      result.put(element.getKey(), element.getValue());
    }
    return result;
  }

}