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Copy pathIxBaseIterator.java
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70 lines (60 loc) · 1.81 KB
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/*
* Copyright 2011-2016 David Karnok
*
* 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 ix;
import java.util.*;
/**
* A base iterator that manages
* the state between hasNext() and the next() calls; plus defines
* the remove() to throw UnsupportedOperationException.
* @param <R> the result value type
*/
public abstract class IxBaseIterator<R> implements Iterator<R> {
/** Indicates a value is available for consumption. */
protected boolean hasValue;
/** Indicates there are no more data available. */
protected boolean done;
/** The current value if hasValue is true. */
protected R value;
/**
* Move the stream forward by a single element.
* @return what the hasNext should return
*/
protected abstract boolean moveNext();
@Override
public final boolean hasNext() {
boolean b = hasValue;
if (!b) {
if (!done) {
return moveNext();
}
}
return b;
}
@Override
public final R next() {
if (!hasValue && !hasNext()) {
throw new NoSuchElementException();
}
R v = value;
hasValue = false;
value = null;
return v;
}
@Override
public void remove() {
throw new UnsupportedOperationException();
}
}