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/*
* Copyright (c) 2009, 2018 Oracle and/or its affiliates. All rights reserved.
*
* This program and the accompanying materials are made available under the
* terms of the Eclipse Public License v. 2.0 which is available at
* http://www.eclipse.org/legal/epl-2.0,
* or the Eclipse Distribution License v. 1.0 which is available at
* http://www.eclipse.org/org/documents/edl-v10.php.
*
* SPDX-License-Identifier: EPL-2.0 OR BSD-3-Clause
*/
// Contributors:
// Oracle - initial API and implementation
//
package org.eclipse.persistence.jpa.jpql.tools.utility.iterable;
import java.util.Arrays;
import java.util.Collection;
import java.util.Iterator;
import org.eclipse.persistence.jpa.jpql.tools.utility.iterator.CloneIterator;
import org.eclipse.persistence.jpa.jpql.utility.CollectionTools;
/**
* A SnapshotCloneIterable returns an iterator on a "snapshot" of a
* collection, allowing for concurrent access to the original collection. A
* copy of the collection is created when the iterable is constructed.
* As a result, the contents of the collection will be the same with
* every call to {@link #iterator()}.
*
* The original collection passed to the SnapshotCloneIterable's
* constructor should be thread-safe (e.g. {@link java.util.Vector});
* otherwise you run the risk of a corrupted collection.
*
* By default, the iterator returned by a SnapshotCloneIterable does not
* support the {@link Iterator#remove()} operation; this is because it does not
* have access to the original collection. But if the SnapshotCloneIterable
* is supplied with a {@link CloneIterator.Remover}
* it will delegate the
* {@link Iterator#remove()} operation to the Remover.
* Alternatively, a subclass can override the iterable's {@link #remove(Object)}
* method.
*
* This iterable is useful for multiple passes over a collection that should not
* be changed (e.g. by another thread) between passes.
*
* @param the type of elements returned by the iterable's iterator
*
* @see CloneIterator
* @see LiveCloneIterable
* @see org.eclipse.persistence.jpa.jpql.utility.iterable.SnapshotCloneListIterable SnapshotCloneListIterable
*/
public class SnapshotCloneIterable extends CloneIterable {
private final Object[] array;
// ********** constructors **********
/**
* Construct a "snapshot" iterable for the specified iterator.
* The {@link Iterator#remove()} operation will not be supported
* by the iterator returned by {@link #iterator()}
* unless a subclass overrides the iterable's {@link #remove(Object)}
* method.
*/
public SnapshotCloneIterable(Iterator iterator) {
super();
this.array = CollectionTools.array(Object.class, iterator);
}
/**
* Construct a "snapshot" iterable for the specified iterator.
* The specified remover will be used by any generated iterators to
* remove objects from the original collection.
*/
public SnapshotCloneIterable(Iterator iterator, CloneIterator.Remover remover) {
super(remover);
this.array =CollectionTools.array(Object.class, iterator);
}
/**
* Construct a "snapshot" iterable for the specified collection.
* The {@link Iterator#remove()} operation will not be supported
* by the iterator returned by {@link #iterator()}
* unless a subclass overrides the iterable's {@link #remove(Object)}
* method.
*/
public SnapshotCloneIterable(Collection collection) {
super();
this.array = collection.toArray();
}
/**
* Construct a "snapshot" iterable for the specified collection.
* The specified remover will be used by any generated iterators to
* remove objects from the original collection.
*/
public SnapshotCloneIterable(Collection collection, CloneIterator.Remover remover) {
super(remover);
this.array = collection.toArray();
}
// ********** Iterable implementation **********
public Iterator iterator() {
return new LocalCloneIterator(this.remover, this.array);
}
@Override
public String toString() {
return Arrays.toString(this.array);
}
// ********** clone iterator **********
/**
* provide access to "internal" constructor
*/
protected static class LocalCloneIterator extends CloneIterator {
protected LocalCloneIterator(Remover remover, Object[] array) {
super(remover, array);
}
}
}