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Simply utility methods used across other Molindo projects
There is a newer version: 3.0.0
/**
 * Copyright 2010 Molindo GmbH
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 * http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package at.molindo.utils.collections;

import static at.molindo.utils.collections.IteratorUtils.iterators;

import java.util.ArrayList;
import java.util.Arrays;
import java.util.Collections;
import java.util.Iterator;
import java.util.List;
import java.util.NoSuchElementException;

public class IteratorChain implements Iterator {

	private final Iterator> _iterators;

	private Iterator _next;
	private Iterator _last;

	public static  Builder builder() {
		return new Builder();
	}

	public static  Builder builder(Class cls) {
		return builder();
	}

	public static  Builder builder(Iterator iter) {
		return new Builder().add(iter);
	}

	public static  Builder builder(Iterable iter) {
		return new Builder().add(iter);
	}

	public static  Builder builder(T o) {
		return new Builder().add(o);
	}

	public static  Builder builder(T... o) {
		return new Builder().add(o);
	}

	public static  IteratorChain chainIterables(Iterable> iterables) {
		return new IteratorChain(iterators(iterables));
	}

	public static  IteratorChain chainIterables(Iterator> iterables) {
		return new IteratorChain(iterators(iterables));
	}

	public IteratorChain(Iterable> iterators) {
		this(iterators.iterator());
	}

	public IteratorChain(Iterator> iterator) {
		// make a copy
		_iterators = IteratorUtils.list(iterator).iterator();

		// init
		if (_iterators.hasNext()) {
			_next = _iterators.next();
		}
	}

	@Override
	public boolean hasNext() {
		if (_next == null) {
			return false;
		} else if (_next.hasNext()) {
			return true;
		} else if (_iterators.hasNext()) {
			_next = _iterators.next();
			return hasNext();
		} else {
			_next = null;
			return false;
		}
	}

	@Override
	public T next() {
		if (_next == null) {
			throw new NoSuchElementException();
		}
		T o = _next.next();
		_last = _next;
		return o;
	}

	@Override
	public void remove() {
		if (_last == null) {
			throw new IllegalStateException("next() has not yet been called");
		}
		_last.remove();
	}

	public static class Builder implements Iterable {

		private final List> _iterators = new ArrayList>();

		private Builder() {
		}

		public Builder add(Iterator iter) {
			_iterators.add(iter);
			return this;
		}

		public Builder add(Iterable iter) {
			return add(iter.iterator());
		}

		public Builder add(T o) {
			return add(Collections.singleton(o).iterator());
		}

		public Builder add(T... o) {
			return add(Arrays.asList(o).iterator());
		}

		public IteratorChain build() {
			return new IteratorChain(_iterators);
		}

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