Main.java Source code

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Here is the source code for Main.java

Source

//package com.java2s;
/*
 * Copyright (c) 2017, 2017, Oracle and/or its affiliates. All rights reserved.
 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
 *
 * This code is free software; you can redistribute it and/or modify it
 * under the terms of the GNU General Public License version 2 only, as
 * published by the Free Software Foundation.
 *
 * This code 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
 * version 2 for more details (a copy is included in the LICENSE file that
 * accompanied this code).
 *
 * You should have received a copy of the GNU General Public License version
 * 2 along with this work; if not, write to the Free Software Foundation,
 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
 *
 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
 * or visit www.oracle.com if you need additional information or have any
 * questions.
 */

import java.util.Arrays;

import java.util.Collections;
import java.util.Iterator;
import java.util.List;
import java.util.Objects;

public class Main {
    /**
     * Concatenates two iterables into a single iterable. The iterator exposed by the returned
     * iterable does not support {@link Iterator#remove()} even if the input iterables do.
     *
     * @throws NullPointerException if {@code a} or {@code b} is {@code null}
     */
    public static <T> Iterable<T> concat(Iterable<T> a, Iterable<T> b) {
        List<Iterable<T>> l = Arrays.asList(a, b);
        return concat(l);
    }

    /**
     * Concatenates multiple iterables into a single iterable. The iterator exposed by the returned
     * iterable does not support {@link Iterator#remove()} even if the input iterables do.
     *
     * @throws NullPointerException if {@code iterables} or any of its elements are {@code null}
     */
    public static <T> Iterable<T> concat(List<Iterable<T>> iterables) {
        for (Iterable<T> iterable : iterables) {
            Objects.requireNonNull(iterable);
        }
        return new Iterable<T>() {
            @Override
            public Iterator<T> iterator() {
                if (iterables.size() == 0) {
                    return Collections.emptyIterator();
                }
                return new Iterator<T>() {
                    Iterator<Iterable<T>> cursor = iterables.iterator();
                    Iterator<T> currentIterator = cursor.next().iterator();

                    private void advance() {
                        while (!currentIterator.hasNext() && cursor.hasNext()) {
                            currentIterator = cursor.next().iterator();
                        }
                    }

                    @Override
                    public boolean hasNext() {
                        advance();
                        return currentIterator.hasNext();
                    }

                    @Override
                    public T next() {
                        advance();
                        return currentIterator.next();
                    }
                };
            }

        };
    }
}