Java tutorial
/**************************************************************** * Licensed to the Apache Software Foundation (ASF) 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.apache.james.jmap.utils; import java.util.List; import java.util.Set; import java.util.function.BinaryOperator; import org.apache.james.jmap.model.Keyword; import org.apache.james.jmap.model.Keywords; import com.github.steveash.guavate.Guavate; import com.google.common.collect.ImmutableList; import com.google.common.collect.Sets; public class KeywordsCombiner implements BinaryOperator<Keywords> { private static final ImmutableList<Keyword> KEYWORD_TO_INTERSECT = ImmutableList.of(Keyword.DRAFT); private static final ImmutableList<Keyword> KEYWORD_NOT_TO_UNION = KEYWORD_TO_INTERSECT; private Keywords.KeywordsFactory keywordsFactory; public KeywordsCombiner() { this.keywordsFactory = Keywords.lenientFactory(); } @Override public Keywords apply(Keywords keywords, Keywords keywords2) { return keywordsFactory .fromSet(Sets.union(union(keywords.getKeywords(), keywords2.getKeywords(), KEYWORD_NOT_TO_UNION), intersect(keywords.getKeywords(), keywords2.getKeywords(), KEYWORD_TO_INTERSECT))); } public Set<Keyword> union(Set<Keyword> set1, Set<Keyword> set2, List<Keyword> exceptKeywords) { return Sets.union(set1, set2).stream().filter(keyword -> !exceptKeywords.contains(keyword)) .collect(Guavate.toImmutableSet()); } public Set<Keyword> intersect(Set<Keyword> set1, Set<Keyword> set2, List<Keyword> forKeywords) { return Sets.intersection(set1, set2).stream().filter(forKeywords::contains) .collect(Guavate.toImmutableSet()); } }