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A lightweight alternative to Java 8 sequential Stream
/*
* Copyright 2016 Daniel Skogquist Åborg
*
* 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 org.d2ab.iterator;
import java.util.Iterator;
import java.util.NoSuchElementException;
/**
* Base class for iterators that map the next element by also peeking at the previous element.
*/
public abstract class BackPeekingMappingIterator extends DelegatingReferenceIterator {
protected T previous;
public BackPeekingMappingIterator(Iterator iterator, T replacement) {
super(iterator);
this.previous = replacement;
}
@Override
public U next() {
if (!hasNext())
throw new NoSuchElementException();
T next = iterator.next();
U mapped = map(previous, next);
previous = next;
return mapped;
}
protected abstract U map(T previous, T next);
}