io.permazen.util.CloseableIterator Maven / Gradle / Ivy
/*
* Copyright (C) 2015 Archie L. Cobbs. All rights reserved.
*/
package io.permazen.util;
import java.io.Closeable;
import java.util.Iterator;
/**
* An {@link Iterator} that is {@link Closeable} and can be {@link Closeable#close close()}'d without
* throwing any exceptions.
*
* @param iteration element type
*/
public interface CloseableIterator extends Iterator, Closeable {
@Override
void close();
/**
* Wrap the given plain {@link Iterator} as necessary to make it a {@link CloseableIterator}.
*
*
* If {@code iterator} already implements {@link CloseableIterator}, then {@code iterator} is returned.
*
*
* If {@code iterator} does not implement {@link CloseableIterator} but does implement {@link Closeable}
* (or {@link AutoCloseable}), then the returned instance will delegate to {@code iterator.close()} when
* {@link Closeable#close close()} is invoked, and any exception thrown will be discarded.
*
*
* Otherwise, invoking {@link Closeable#close close()} on the returned instance does nothing.
*
* @param iterator nested iterator
* @param iteration element type
* @return {@link CloseableIterator} wrapping {@code iterator}, or null if {@code iterator} is null
*/
static CloseableIterator wrap(final Iterator iterator) {
if (iterator == null)
return null;
if (iterator instanceof CloseableIterator)
return (CloseableIterator)iterator;
return new CloseableIteratorWrapper<>(iterator, iterator instanceof AutoCloseable ? (AutoCloseable)iterator : null);
}
/**
* Wrap the given plain {@link Iterator} to make it a {@link CloseableIterator}, such that when
* {@link Closeable#close close()} is invoked, the associated {@code resource} is closed.
*
* @param iterator nested iterator
* @param resource resource to close when the returned instance is {@link Closeable#close close()}'d,
* or null to do nothing on {@link Closeable#close close()}
* @param iteration element type
* @return {@link CloseableIterator} wrapping {@code iterator}, or null if {@code iterator} is null
*/
static CloseableIterator wrap(final Iterator iterator, AutoCloseable resource) {
if (iterator == null)
return null;
return new CloseableIteratorWrapper<>(iterator, resource);
}
}