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SciJava Common is a shared library for SciJava software. It provides a plugin framework, with an extensible mechanism for service discovery, backed by its own annotation processor, so that plugins can be loaded dynamically. It is used by downstream projects in the SciJava ecosystem, such as ImageJ and SCIFIO.

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/*
 * #%L
 * SciJava Common shared library for SciJava software.
 * %%
 * Copyright (C) 2009 - 2017 Board of Regents of the University of
 * Wisconsin-Madison, Broad Institute of MIT and Harvard, Max Planck
 * Institute of Molecular Cell Biology and Genetics, University of
 * Konstanz, and KNIME GmbH.
 * %%
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions are met:
 * 
 * 1. Redistributions of source code must retain the above copyright notice,
 *    this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright notice,
 *    this list of conditions and the following disclaimer in the documentation
 *    and/or other materials provided with the distribution.
 * 
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
 * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDERS OR CONTRIBUTORS BE
 * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
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package org.scijava.util;

import java.util.Enumeration;
import java.util.Iterator;

/**
 * A class that provides more thorough support for iteration. Any
 * {@link Enumeration}, {@link Iterator} or {@link Iterable} object can be
 * provided to the constructor, and the resultant {@code IteratorPlus} will
 * provide all three access mechanisms. In the case of {@link #iterator()} it
 * simply returns {@code this}, for more convenient usage with for-each loops. Note, however, that because of this fact, multiple calls
 * to {#iterator()} will produce the same {@link Iterator} every time (in fact,
 * the {@link IteratorPlus} object itself).
 * 
 * For example, let's say you have an {@code Enumeration} and you want
 * to loop over it with the for-each syntax. You could write:
 * 
 * {@code
 * final Enumeration en = ...;
 * for (final String s : new IteratorPlus(en))
 *   // do something with the string
 * }
 * 
 * The same technique works with {@link Iterator}.
 * 
 * 
 * @author Curtis Rueden
 */
public class IteratorPlus implements Enumeration, Iterator,
	Iterable
{

	/** The backing {@link Iterator}. */
	private final Iterator iterator;

	// -- Constructors --

	public IteratorPlus(final Iterable iterable) {
		this(iterable.iterator());
	}

	public IteratorPlus(final Enumeration enumeration) {
		this(new EnumerationIterator<>(enumeration));
	}

	public IteratorPlus(final Iterator iterator) {
		this.iterator = iterator;
	}

	// -- Enumeration methods --

	@Override
	public boolean hasMoreElements() {
		return hasNext();
	}

	@Override
	public E nextElement() {
		return next();
	}

	// -- Iterator methods --

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

	@Override
	public E next() {
		return iterator.next();
	}

	@Override
	public void remove() {
		iterator.remove();
	}

	// -- Iterable methods --

	@Override
	public Iterator iterator() {
		return this;
	}

	// -- Helper classes --

	/**
	 * A helper class for translating an {@link Enumeration} into an
	 * {@link Iterator}.
	 */
	private static class EnumerationIterator implements Iterator {

		private final Enumeration enumeration;

		private EnumerationIterator(final Enumeration enumeration) {
			this.enumeration = enumeration;
		}

		@Override
		public boolean hasNext() {
			return enumeration.hasMoreElements();
		}

		@Override
		public E next() {
			return enumeration.nextElement();
		}

		@Override
		public void remove() {
			throw new UnsupportedOperationException();
		}
	}

}