001    /*
002     * Licensed to the Apache Software Foundation (ASF) under one or more
003     * contributor license agreements.  See the NOTICE file distributed with
004     * this work for additional information regarding copyright ownership.
005     * The ASF licenses this file to You under the Apache License, Version 2.0
006     * (the "License"); you may not use this file except in compliance with
007     * the License.  You may obtain a copy of the License at
008     *
009     *     http://www.apache.org/licenses/LICENSE-2.0
010     *
011     * Unless required by applicable law or agreed to in writing, software
012     * distributed under the License is distributed on an "AS IS" BASIS,
013     * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
014     * See the License for the specific language governing permissions and
015     * limitations under the License.
016     */
017    package org.apache.commons.collections.primitives.adapters.io;
018    
019    import java.io.IOException;
020    import java.io.Reader;
021    import java.util.NoSuchElementException;
022    
023    import org.apache.commons.collections.primitives.CharIterator;
024    
025    /**
026     * Adapts a {@link Reader} to the {@link CharIterator} interface.
027     * 
028     * @version $Revision: 480462 $ $Date: 2006-11-29 09:15:00 +0100 (Wed, 29 Nov 2006) $
029     * @author Rodney Waldhoff
030     */
031    public class ReaderCharIterator implements CharIterator {
032    
033        public ReaderCharIterator(Reader in) {
034            this.reader = in;
035        }
036    
037        public static CharIterator adapt(Reader in) {
038            return null == in ? null : new ReaderCharIterator(in);
039        }
040        
041        public boolean hasNext() {
042            ensureNextAvailable();
043            return (-1 != next);
044        }
045    
046        public char next() {
047            if(!hasNext()) {
048                throw new NoSuchElementException("No next element");
049            } else {
050                nextAvailable = false;
051                return (char)next;
052            }
053        }
054        
055        /**
056         * Not supported.
057         * @throws UnsupportedOperationException
058         */
059        public void remove() throws UnsupportedOperationException {
060            throw new UnsupportedOperationException("remove() is not supported here");
061        }
062    
063        private void ensureNextAvailable() {
064            if(!nextAvailable) {
065                readNext();
066            }
067        }
068    
069        private void readNext() {
070            try {
071                next = reader.read();
072                nextAvailable = true;
073            } catch(IOException e) {
074                // TODO: Use a tunnelled exception instead? 
075                // See http://radio.weblogs.com/0122027/2003/04/01.html#a7, for example            
076                throw new RuntimeException(e.toString());
077            }
078        }
079        
080        private Reader reader = null;
081        private boolean nextAvailable = false;
082        private int next;
083    
084    }