001package ball.util.stream; 002/*- 003 * ########################################################################## 004 * Utilities 005 * $Id: Permutations.java 5285 2020-02-05 04:23:21Z ball $ 006 * $HeadURL: svn+ssh://svn.hcf.dev/var/spool/scm/repository.svn/ball-util/trunk/src/main/java/ball/util/stream/Permutations.java $ 007 * %% 008 * Copyright (C) 2008 - 2020 Allen D. Ball 009 * %% 010 * Licensed under the Apache License, Version 2.0 (the "License"); 011 * you may not use this file except in compliance with the License. 012 * You may obtain a copy of the License at 013 * 014 * http://www.apache.org/licenses/LICENSE-2.0 015 * 016 * Unless required by applicable law or agreed to in writing, software 017 * distributed under the License is distributed on an "AS IS" BASIS, 018 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 019 * See the License for the specific language governing permissions and 020 * limitations under the License. 021 * ########################################################################## 022 */ 023import java.util.Collection; 024import java.util.List; 025import java.util.function.Predicate; 026import java.util.stream.Stream; 027 028/** 029 * {@link Stream} implementaion that provides all permutations of a 030 * {@link List}. 031 * 032 * @param <T> The {@link List} element type. 033 * 034 * @author {@link.uri mailto:ball@hcf.dev Allen D. Ball} 035 * @version $Revision: 5285 $ 036 */ 037public interface Permutations<T> extends Combinations<T> { 038 039 /** 040 * Method to get the {@link Stream} of permutations. 041 * 042 * @param collection The {@link Collection} of elements to 043 * permute. 044 * @param <T> The {@link Collection} element type. 045 * 046 * @return The {@link Stream} of permutations. 047 */ 048 public static <T> Stream<List<T>> of(Collection<T> collection) { 049 return of(null, collection); 050 } 051 052 /** 053 * Method to get the {@link Stream} of permutations. 054 * 055 * @param predicate The optional {@link Predicate} (may be 056 * {@code null}) specifying prerequisite 057 * requirement(s) for the combinations. Any 058 * path that does not match will be pruned. 059 * @param collection The {@link Collection} of elements to 060 * permute. 061 * @param <T> The {@link Collection} element type. 062 * 063 * @return The {@link Stream} of permutations. 064 */ 065 public static <T> Stream<List<T>> of(Predicate<List<T>> predicate, 066 Collection<T> collection) { 067 int size = collection.size(); 068 069 return Combinations.of(size, size, predicate, collection); 070 } 071}