/*
 * Copyright (c) 2008 Harold Cooper. All rights reserved.
 * Licensed under the MIT License.
 * See LICENSE file in the project root for full license information.
 */

package org.pcollections;

import java.util.Collection;

A static convenience class for creating efficient persistent sets.
This class simply creates MapPSets backed by HashTreePMaps.
Author:
harold/**
 * A static convenience class for creating efficient persistent sets.
 *
 * <p>This class simply creates MapPSets backed by HashTreePMaps.
 *
 * @author harold
 */
public final class HashTreePSet {
  // not instantiable (or subclassable):
  private HashTreePSet() {}

  private static final MapPSet<Object> EMPTY = MapPSet.from(HashTreePMap.empty());

  
Type parameters:
<E> – 
Returns:
an empty set/**
   * @param <E>
   * @return an empty set
   */
  @SuppressWarnings("unchecked")
  public static <E> MapPSet<E> empty() {
    return (MapPSet<E>) EMPTY;
  }

  
Params:
e – 
Type parameters:
<E> – 
Returns:
empty().plus(e)/**
   * @param <E>
   * @param e
   * @return empty().plus(e)
   */
  public static <E> MapPSet<E> singleton(final E e) {
    return HashTreePSet.<E>empty().plus(e);
  }

  
Params:
list – 
Type parameters:
<E> – 
Returns:
empty().plusAll(map)/**
   * @param <E>
   * @param list
   * @return empty().plusAll(map)
   */
  public static <E> MapPSet<E> from(final Collection<? extends E> list) {
    return HashTreePSet.<E>empty().plusAll(list);
  }
}