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/*
 * Copyright (C) 2010 The Guava Authors
 *
 * 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 jersey.repackaged.com.google.common.collect;

import jersey.repackaged.com.google.common.annotations.GwtCompatible;

import java.util.NoSuchElementException;

import javax.annotation.Nullable;

/**
 * This class provides a skeletal implementation of the {@code Iterator}
 * interface for sequences whose next element can always be derived from the
 * previous element. Null elements are not supported, nor is the
 * {@link #remove()} method.
 *
 * 

Example:

   {@code
 *
 *   Iterator powersOfTwo = 
 *       new AbstractSequentialIterator(1) {
 *         protected Integer computeNext(Integer previous) {
 *           return (previous == 1 << 30) ? null : previous * 2;
 *         }
 *       };}
* * @author Chris Povirk * @since 12.0 (in Guava as {@code AbstractLinkedIterator} since 8.0) */ @GwtCompatible public abstract class AbstractSequentialIterator extends UnmodifiableIterator { private T nextOrNull; /** * Creates a new iterator with the given first element, or, if {@code * firstOrNull} is null, creates a new empty iterator. */ protected AbstractSequentialIterator(@Nullable T firstOrNull) { this.nextOrNull = firstOrNull; } /** * Returns the element that follows {@code previous}, or returns {@code null} * if no elements remain. This method is invoked during each call to * {@link #next()} in order to compute the result of a future call to * {@code next()}. */ protected abstract T computeNext(T previous); @Override public final boolean hasNext() { return nextOrNull != null; } @Override public final T next() { if (!hasNext()) { throw new NoSuchElementException(); } try { return nextOrNull; } finally { nextOrNull = computeNext(nextOrNull); } } }




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