jpa/org.eclipse.persistence.jpa.jpql/src/main/java/org/eclipse/persistence/jpa/jpql/tools/utility/iterable/SingleElementListIterable.java

/*
 * Copyright (c) 2009, 2021 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.ListIterator;
import org.eclipse.persistence.jpa.jpql.tools.utility.iterator.SingleElementListIterator;
import org.eclipse.persistence.jpa.jpql.utility.iterable.ListIterable;

/**
 * A <code>SingleElementListIterable</code> returns a {@link ListIterator}
 * that holds a single element
 * and returns it with the first call to {@link ListIterator#next()}, at
 * which point it will return <code>false</code> to any subsequent
 * call to {@link ListIterator#hasNext()}. Likewise, it will return <code>false</code>
 * to a call to {@link ListIterator#hasPrevious()} until a call to {@link ListIterator#next()},
 * at which point a call to {@link ListIterator#previous()} will return the
 * single element.
 * <p>
 * A <code>SingleElementListIterable</code> is equivalent to the
 * {@link Iterable} returned by:
 *     {@link java.util.Collections#singletonList(Object)}.
 *
 * @param <E> the type of elements returned by the list iterable's list iterator
 *
 * @see SingleElementListIterator
 * @see <a href="http://git.eclipse.org/c/dali/webtools.dali.git/tree/common/plugins/org.eclipse.jpt.common.utility/src/org/eclipse/jpt/common/utility/internal/iterable/SingleElementListIterable.java">SingleElementListIterable</a>
 */
@SuppressWarnings("nls")
public class SingleElementListIterable<E> implements ListIterable<E> {

    private final E element;

    /**
     * Construct a list iterable that contains only the specified element.
     */
    public SingleElementListIterable(E element) {
        super();
        this.element = element;
    }

    @Override
    public ListIterator<E> iterator() {
        return new SingleElementListIterator<>(this.element);
    }

    @Override
    public String toString() {
        return "[" + this.element + "]";
    }
}