89 lines
1.9 KiB
Java
89 lines
1.9 KiB
Java
/*
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* Copyright (C) 2007 The Guava Authors
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*
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* Licensed under the Apache License, Version 2.0 (the "License");
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* you may not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*/
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package com.google.common.base;
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import static com.google.common.base.Preconditions.checkState;
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import java.util.Iterator;
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import java.util.NoSuchElementException;
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import com.google.common.annotations.GwtCompatible;
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/**
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* Note this class is a copy of
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* {@link com.google.common.collect.AbstractIterator} (for dependency reasons).
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*/
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@GwtCompatible
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abstract class AbstractIterator<T> implements Iterator<T> {
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private State state = State.NOT_READY;
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protected AbstractIterator() {
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}
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private enum State {
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READY, NOT_READY, DONE, FAILED,
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}
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private T next;
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protected abstract T computeNext();
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protected final T endOfData() {
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state = State.DONE;
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return null;
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}
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@Override
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public final boolean hasNext() {
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checkState(state != State.FAILED);
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switch (state) {
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case DONE:
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return false;
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case READY:
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return true;
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default:
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}
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return tryToComputeNext();
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}
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private boolean tryToComputeNext() {
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state = State.FAILED; // temporary pessimism
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next = computeNext();
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if (state != State.DONE) {
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state = State.READY;
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return true;
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}
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return false;
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}
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@Override
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public final T next() {
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if (!hasNext()) {
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throw new NoSuchElementException();
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}
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state = State.NOT_READY;
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T result = next;
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next = null;
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return result;
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}
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@Override
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public final void remove() {
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throw new UnsupportedOperationException();
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}
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}
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