| /* |
| * Copyright (c) 2006, 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.iterator; |
| |
| import java.util.Iterator; |
| import java.util.NoSuchElementException; |
| |
| /** |
| * A <code>null</code> instance of an {@link Iterator}. |
| * |
| * @version 2.4 |
| * @since 2.4 |
| */ |
| @SuppressWarnings("nls") |
| public final class EmptyIterator implements Iterator<Object> { |
| |
| /** |
| * The singleton instance this <code>EmptyIterator</code>. |
| */ |
| private static EmptyIterator INSTANCE = new EmptyIterator(); |
| |
| /** |
| * Ensure non-instantiability. |
| */ |
| private EmptyIterator() { |
| super(); |
| } |
| |
| /** |
| * Returns the singleton instance this <code>EmptyIterator</code>. |
| * |
| * @return The singleton instance this <code>EmptyIterator</code> |
| */ |
| @SuppressWarnings("unchecked") |
| public static synchronized <T> Iterator<T> instance() { |
| return (Iterator<T>) INSTANCE; |
| } |
| |
| @Override |
| public boolean hasNext() { |
| return false; |
| } |
| |
| @Override |
| public Object next() { |
| throw new NoSuchElementException("A NullIterator is read-only."); |
| } |
| |
| @Override |
| public void remove() { |
| throw new UnsupportedOperationException("A NullIterator is read-only."); |
| } |
| |
| @Override |
| public String toString() { |
| return getClass().getSimpleName(); |
| } |
| } |