union Of List Of Lists - Java Collection Framework

Java examples for Collection Framework:List

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Description

union Of List Of Lists

Demo Code

/*/*from w  ww.jav  a2 s. c  o  m*/
 * Copyright (C) 2013
 *
 * 52?North Initiative for Geospatial Open Source Software GmbH
 * Contact: Andreas Wytzisk
 * Martin-Luther-King-Weg 24
 * 48155 Muenster, Germany
 * info@52north.org
 *
 * All rights reserved. This program and the accompanying materials
 * are made available under the terms of the Eclipse Public License v1.0
 * which accompanies this distribution, and is available at
 * http://www.eclipse.org/legal/epl-v10.html
 */
//package com.java2s;
import java.util.ArrayList;

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

import java.util.HashSet;
import java.util.LinkedList;
import java.util.List;
import java.util.Map;

import java.util.Set;

public class Main {
    public static void main(String[] argv) {
        Collection collectionOfCollection = java.util.Arrays.asList("asdf",
                "java2s.com");
        System.out.println(unionOfListOfLists(collectionOfCollection));
    }

    /**
     * @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(
            final Collection<? extends Collection<T>> collectionOfCollection) {
        if (collectionOfCollection == null
                || collectionOfCollection.isEmpty()) {
            return new HashSet<T>(0);
        }
        final HashSet<T> union = new HashSet<T>();
        for (final Collection<T> col : collectionOfCollection) {
            if (col != null) {
                for (final T t : col) {
                    if (t != null) {
                        union.add(t);
                    }
                }
            }
        }
        return union;
    }

    public static <T> List<T> asList(final Iterable<? extends T> iterable) {
        return (iterable instanceof Collection) ? new LinkedList<T>(
                (Collection<? extends T>) iterable) : new LinkedList<T>() {
            private static final long serialVersionUID = 3109256773218160485L;
            {
                if (iterable != null) {
                    for (final T t : iterable) {
                        add(t);
                    }
                }
            }
        };
    }

    public static <T> List<T> asList(final T t, final T... ts) {
        final ArrayList<T> list = new ArrayList<T>(ts.length + 1);
        list.add(t);
        Collections.addAll(list, ts);
        return list;
    }

    /**
     * Check if collection is not <tt>null</tt> and empty
     * 
     * @param collection
     *          Collection to check
     * 
     * @return <tt>true</tt>, if collection is not null and empty, else <tt>false</tt>
     */
    public static <T> boolean isEmpty(final Collection<T> collection) {
        return collection != null && collection.isEmpty();
    }

    /**
     * Check if map is not <tt>null</tt> and empty
     * 
     * @param map
     *          map to check
     * 
     * @return <tt>true</tt>, if map is not null and empty, else <tt>false</tt>
     */
    public static <K, V> boolean isEmpty(final Map<K, V> map) {
        return map != null && map.isEmpty();
    }
}

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