Java tutorial
//package com.java2s; /* * CrimsonGlow is an adult computer roleplaying game with spanking content. * Copyright (C) 2015 Andrew Russell * * This program is free software: you can redistribute it and/or modify * it under the terms of the GNU General Public License as published by * the Free Software Foundation, either version 3 of the License, or * (at your option) any later version. * * This program is distributed in the hope that it will be useful, * but WITHOUT ANY WARRANTY; without even the implied warranty of * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the * GNU General Public License for more details. * * You should have received a copy of the GNU General Public License * along with this program. If not, see <http://www.gnu.org/licenses/>. * */ import java.util.LinkedHashMap; import java.util.function.Function; import java.util.stream.Collector; import java.util.stream.Collectors; public class Main { public static <T, K, U> Collector<T, ?, LinkedHashMap<K, U>> toLinkedHashMap( Function<? super T, ? extends K> keyMapper, Function<? super T, ? extends U> valueMapper) { return Collectors.toMap(keyMapper, valueMapper, (u, v) -> { throw new IllegalStateException(String.format("Duplicate key %s", u)); }, LinkedHashMap::new); } }