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Basic utility library containing several useful classes (e.g., a Pair class) to ease everyday programming.

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/* Copyright (C) 2013 TU Dortmund
 * This file is part of AutomataLib, http://www.automatalib.net/.
 * 
 * AutomataLib is free software; you can redistribute it and/or
 * modify it under the terms of the GNU Lesser General Public
 * License version 3.0 as published by the Free Software Foundation.
 * 
 * AutomataLib 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
 * Lesser General Public License for more details.
 * 
 * You should have received a copy of the GNU Lesser General Public
 * License along with AutomataLib; if not, see
 * http://www.gnu.de/documents/lgpl.en.html.
 */
package net.automatalib.commons.util.collections;

import java.util.Iterator;
import java.util.NoSuchElementException;

public abstract class IterableUtil {
	
	private static final Iterator EMPTY_ITERATOR = new Iterator() {
		/*
		 * (non-Javadoc)
		 * @see java.util.Iterator#hasNext()
		 */
		@Override
		public boolean hasNext() {
			return false;
		}

		/*
		 * (non-Javadoc)
		 * @see java.util.Iterator#next()
		 */
		@Override
		public Object next() {
			throw new NoSuchElementException();
		}

		/*
		 * (non-Javadoc)
		 * @see java.util.Iterator#remove()
		 */
		@Override
		public void remove() {
			throw new UnsupportedOperationException();
		}
		
	};
	
	@SafeVarargs
	public static  Iterator concat(Iterator ...iterators) {
		return new ConcatIterator<>(iterators);
	}
	
	@SafeVarargs
	public static  Iterable concat(final Iterable ...iterables) {
		return new Iterable() {
			@Override
			public Iterator iterator() {
				@SuppressWarnings("unchecked")
				Iterator[] iterators = new Iterator[iterables.length];
				for(int i = 0; i < iterables.length; i++)
					iterators[i] = iterables[i].iterator();
				return concat(iterators);
			}
		};
	}
	
	@SuppressWarnings("unchecked")
	public static  Iterator emptyIterator() {
		return (Iterator)EMPTY_ITERATOR;
	}
	
	public static  Iterator unmodifiableIterator(Iterator iterator) {
		return new UnmodifiableIterator<>(iterator);
	}
	
	
	public static  Iterable unmodifiableIterable(final Iterable iterable) {
		return new Iterable() {
			@Override
			public Iterator iterator() {
				return unmodifiableIterator(iterable.iterator());
			}
		};
	}
	
	// Prevent inheritance
	private IterableUtil() {}

}
 















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