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Diffstat (limited to 'guava/src/com/google/common/collect/AbstractLinkedIterator.java')
-rw-r--r-- | guava/src/com/google/common/collect/AbstractLinkedIterator.java | 84 |
1 files changed, 84 insertions, 0 deletions
diff --git a/guava/src/com/google/common/collect/AbstractLinkedIterator.java b/guava/src/com/google/common/collect/AbstractLinkedIterator.java new file mode 100644 index 0000000..8e722dd --- /dev/null +++ b/guava/src/com/google/common/collect/AbstractLinkedIterator.java @@ -0,0 +1,84 @@ +/* + * 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 com.google.common.collect; + +import com.google.common.annotations.Beta; +import 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. + * + * <p>Example: <pre> {@code + * + * Iterator<Integer> powersOfTwo = new AbstractLinkedIterator<Integer>(1) { + * protected Integer computeNext(Integer previous) { + * return (previous == 1 << 30) ? null : previous * 2; + * } + * };}</pre> + * + * @author Chris Povirk + * @since 8.0 + * @deprecated This class has been renamed {@link AbstractSequentialIterator}. + * This class is scheduled to be removed in Guava release 13.0. + */ +@Beta +@Deprecated +@GwtCompatible +public abstract class AbstractLinkedIterator<T> + extends UnmodifiableIterator<T> { + private T nextOrNull; + + /** + * Creates a new iterator with the given first element, or, if {@code + * firstOrNull} is null, creates a new empty iterator. + */ + protected AbstractLinkedIterator(@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 <i>future</i> 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); + } + } +} |