htsjdk.samtools.util.AbstractIterator Maven / Gradle / Ivy
/*
* The MIT License
*
* Copyright (c) 2011 The Broad Institute
*
* Permission is hereby granted, free of charge, to any person obtaining a copy
* of this software and associated documentation files (the "Software"), to deal
* in the Software without restriction, including without limitation the rights
* to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
* copies of the Software, and to permit persons to whom the Software is
* furnished to do so, subject to the following conditions:
*
* The above copyright notice and this permission notice shall be included in
* all copies or substantial portions of the Software.
*
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
* AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
* OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
* THE SOFTWARE.
*/
package htsjdk.samtools.util;
import java.util.Iterator;
import java.util.NoSuchElementException;
/**
* Base class of implementing iterators. All you have to do is implement advance which gets
* the next element.
*
* @author Doug Voet (dvoet at broadinstitute dot org)
*/
public abstract class AbstractIterator implements Iterator {
protected E next;
private boolean iterating = false;
@Override
public boolean hasNext() {
// If this is the start of iteration, queue up the first item
if (!iterating) {
next = advance();
iterating = true;
}
return next != null;
}
@Override
public E next() {
if (!hasNext()) {
throw new NoSuchElementException();
}
E ret = next;
next = advance();
return ret;
}
@Override
public void remove() {
throw new UnsupportedOperationException("Remove() not supported.");
}
/**
* @return the next element or null if the iterator is at the end
*/
protected abstract E advance();
/**
* Returns the next element in the iterator, if one exists. Otherwise, returns null. Invoking this method does not advance the iterator.
* @return The next element in the iterator, without advancing, or, if no other element exists, null.
*/
public E peek() {
return next;
}
/**
* @return true after the first time hasNext() or next() have been called
*/
protected boolean isIterating() {
return iterating;
}
}