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Java example source code file (ReaderCharacterIterator.java)

This example Java source code file (ReaderCharacterIterator.java) is included in the alvinalexander.com "Java Source Code Warehouse" project. The intent of this project is to help you "Learn Java by Example" TM.

Learn more about this Java project at its project page.

Java - Java tags/keywords

eof, ioexception, readercharacteriterator, string, stringbuffer

The ReaderCharacterIterator.java Java example source code

/*
 * reserved comment block
 * DO NOT REMOVE OR ALTER!
 */
/*
 * Copyright 1999-2004 The Apache Software Foundation.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package com.sun.org.apache.regexp.internal;

import java.io.Reader;
import java.io.IOException;

/**
 * Encapsulates java.io.Reader as CharacterIterator
 *
 * @author <a href="mailto:ales.novak@netbeans.com">Ales Novak
 */
public final class ReaderCharacterIterator implements CharacterIterator
{
    /** Underlying reader */
    private final Reader reader;

    /** Buffer of read chars */
    private final StringBuffer buff;

    /** read end? */
    private boolean closed;

    /** @param reader a Reader, which is parsed */
    public ReaderCharacterIterator(Reader reader)
    {
        this.reader = reader;
        this.buff = new StringBuffer(512);
        this.closed = false;
    }

    /** @return a substring */
    public String substring(int beginIndex, int endIndex)
    {
        try
        {
            ensure(endIndex);
            return buff.toString().substring(beginIndex, endIndex);
        }
        catch (IOException e)
        {
            throw new StringIndexOutOfBoundsException(e.getMessage());
        }
    }

    /** @return a substring */
    public String substring(int beginIndex)
    {
        try
        {
            readAll();
            return buff.toString().substring(beginIndex);
        }
        catch (IOException e)
        {
            throw new StringIndexOutOfBoundsException(e.getMessage());
        }
    }

    /** @return a character at the specified position. */
    public char charAt(int pos)
    {
        try
        {
            ensure(pos);
            return buff.charAt(pos);
        }
        catch (IOException e)
        {
            throw new StringIndexOutOfBoundsException(e.getMessage());
        }
    }

    /** @return <tt>true iff if the specified index is after the end of the character stream */
    public boolean isEnd(int pos)
    {
        if (buff.length() > pos)
        {
            return false;
        }
        else
        {
            try
            {
                ensure(pos);
                return (buff.length() <= pos);
            }
            catch (IOException e)
            {
                throw new StringIndexOutOfBoundsException(e.getMessage());
            }
        }
    }

    /** Reads n characters from the stream and appends them to the buffer */
    private int read(int n) throws IOException
    {
        if (closed)
        {
            return 0;
        }

        char[] c = new char[n];
        int count = 0;
        int read = 0;

        do
        {
            read = reader.read(c);
            if (read < 0) // EOF
            {
                closed = true;
                break;
            }
            count += read;
            buff.append(c, 0, read);
        }
        while (count < n);

        return count;
    }

    /** Reads rest of the stream. */
    private void readAll() throws IOException
    {
        while(! closed)
        {
            read(1000);
        }
    }

    /** Reads chars up to the idx */
    private void ensure(int idx) throws IOException
    {
        if (closed)
        {
            return;
        }

        if (idx < buff.length())
        {
            return;
        }
        read(idx + 1 - buff.length());
    }
}

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