Main.java Source code

Introduction

Here is the source code for Main.java

Source

//package com.java2s;
/**
 * Copyright (C) 2012-2015 52North Initiative for Geospatial Open Source
 * Software GmbH
 *
 * This program is free software; you can redistribute it and/or modify it
 * under the terms of the GNU General Public License version 2 as published
 * by the Free Software Foundation.
 *
 * If the program is linked with libraries which are licensed under one of
 * the following licenses, the combination of the program with the linked
 * library is not considered a "derivative work" of the program:
 *
 *     - Apache License, version 2.0
 *     - Apache Software License, version 1.0
 *     - GNU Lesser General Public License, version 3
 *     - Mozilla Public License, versions 1.0, 1.1 and 2.0
 *     - Common Development and Distribution License (CDDL), version 1.0
 *
 * Therefore the distribution of the program linked with libraries licensed
 * under the aforementioned licenses, is permitted by the copyright holders
 * if the distribution is compliant with both the GNU General Public
 * License version 2 and the aforementioned licenses.
 *
 * 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.
 */

import static java.util.stream.Collectors.toSet;

import java.util.Arrays;
import java.util.Collection;
import java.util.Collections;

import java.util.Map;
import java.util.Map.Entry;
import java.util.Objects;
import java.util.Optional;
import java.util.Set;

import java.util.stream.Collectors;
import java.util.stream.Stream;

public class Main {
    /**
     * @param collectionOfCollection
     *            a Collection<Collection<T>>
     *
     * @return a Set<T> containing all values of all Collections<T>
     *         without any duplicates
     */
    public static <T> Set<T> unionOfListOfLists(
            Collection<? extends Collection<? extends T>> collectionOfCollection) {
        return Optional.ofNullable(collectionOfCollection).map(Collection::stream).orElseGet(Stream::empty)
                .filter(Objects::nonNull).flatMap(x -> x.stream()).filter(Objects::nonNull).collect(toSet());
    }

    /**
     * @param entries
     *            the <i>final</i> set of entries to add to the newly created
     *            <i>unmodifiable</i> map
     * @return an <i>unmodifiable</i> map with all given entries
     */
    @SafeVarargs
    public static <K, V> Map<K, V> map(Entry<K, V>... entries) {
        return Collections
                .unmodifiableMap(Arrays.stream(entries).collect(Collectors.toMap(Entry::getKey, Entry::getValue)));
    }

    /**
     * @param <K> the key type
     * @param <V> the value type
     * @param m the map
     * @return an <b>UNMODIFIABLE</b> Map&lt;K, V&gt;
     */
    public static <K, V> Map<K, V> unmodifiableMap(Map<? extends K, ? extends V> m) {
        return Optional.ofNullable(m).map(Collections::unmodifiableMap).orElseGet(Collections::emptyMap);
    }
}