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 */
017package org.apache.commons.collections.primitives.adapters.io;
018
019import java.io.IOException;
020import java.io.Reader;
021import java.util.NoSuchElementException;
022
023import 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 03:15:00 -0500 (Wed, 29 Nov 2006) $
029 * @author Rodney Waldhoff
030 */
031public 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}