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Core interfaces and classes for Apache Commons Geometry.
/*
* Licensed to the Apache Software Foundation (ASF) under one or more
* contributor license agreements. See the NOTICE file distributed with
* this work for additional information regarding copyright ownership.
* The ASF licenses this file to You 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 org.apache.commons.geometry.core.internal;
import java.util.Collection;
import java.util.Deque;
import java.util.Iterator;
import java.util.LinkedList;
import java.util.NoSuchElementException;
/** Class that wraps another iterator, converting each input iterator value into
* one or more output iterator values.
* @param Input iterator type
* @param Output iterator type
*/
public abstract class IteratorTransform implements Iterator {
/** Input iterator instance that supplies the input values for this instance. */
private final Iterator inputIterator;
/** Output value queue. */
private final Deque outputQueue = new LinkedList<>();
/** Create a new instance that uses the given iterator as the input source.
* @param inputIterator iterator supplying input values
*/
public IteratorTransform(final Iterator inputIterator) {
this.inputIterator = inputIterator;
}
/** {@inheritDoc} */
@Override
public boolean hasNext() {
return loadNextOutput();
}
/** {@inheritDoc} */
@Override
public T next() {
if (outputQueue.isEmpty()) {
throw new NoSuchElementException();
}
return outputQueue.removeFirst();
}
/** Load the next output values into the output queue. Returns true if the output queue
* contains more entries.
* @return true if more output values are available
*/
private boolean loadNextOutput() {
while (outputQueue.isEmpty() && inputIterator.hasNext()) {
acceptInput(inputIterator.next());
}
return !outputQueue.isEmpty();
}
/** Add a value to the output queue.
* @param value value to add to the output queue
*/
protected void addOutput(final T value) {
outputQueue.add(value);
}
/** Add multiple values to the output queue.
* @param values values to add to the output queue
*/
protected void addAllOutput(final Collection values) {
outputQueue.addAll(values);
}
/** Accept a value from the input iterator. This method should take
* the input value and add one or more values to the output queue.
* @param input value from the input iterator
*/
protected abstract void acceptInput(I input);
}