public StreamCharacterIterator(InputStream is) 
{
        this.is = is;
        this.buff = new StringBuffer(512);
        this.closed = false;
}

Parameters:

is - an InputStream, which is parsed

 public char charAt(int pos) 
{
        try
        {
            ensure(pos);
            return buff.charAt(pos);
        }
        catch (IOException e)
        {
            throw new StringIndexOutOfBoundsException(e.getMessage());
        }
}

 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());
            }
        }
}

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

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