public Ptg() 
{

}

Creates new Ptg

 public static Ptg createPtg(byte[] data,
    int offset) 
{
        byte id     = data[ offset + 0 ];
        Ptg  retval = null;
        System.out.println("PTG = " + Integer.toHexString(id) + " (" + id
                           + ")");
        switch (id)
        {
            case AddPtg.sid :
                retval = new AddPtg(data, offset);
                break;
            case SubtractPtg.sid :
                retval = new SubtractPtg(data, offset);
                break;
            case IntPtg.sid :
                retval = new IntPtg(data, offset);
                break;
            case DividePtg.sid :
                retval = new DividePtg(data, offset);
                break;
            case MultiplyPtg.sid :
                retval = new MultiplyPtg(data, offset);
                break;
            case PowerPtg.sid :
                retval = new PowerPtg(data, offset);
                break;
            case AreaPtg.sid :
                retval = new AreaPtg(data, offset);
                break;
            case MemErrPtg.sid :
                retval = new MemErrPtg(data, offset);
                break;
            case AttrPtg.sid :
                retval = new AttrPtg(data, offset);
                break;
            case ValueReferencePtg.sid :
                retval = new ValueReferencePtg(data, offset);
                break;
            case ParenthesisPtg.sid :
                retval = new ParenthesisPtg(data, offset);
                break;
            case ValueVariableFunctionPtg.sid :
                retval = new ValueVariableFunctionPtg(data, offset);
                break;
            case NamePtg.sid :
                retval = new NamePtg(data, offset);
                break;
            case ExpPtg.sid :
                retval = new ExpPtg(data, offset);
                break;
            default :
                // retval = new UnknownPtg();
                throw new RuntimeException("Unknown PTG = "
                                           + Integer.toHexString(( int ) id)
                                           + " (" + ( int ) id + ")");
        }
        return retval;
}

 public final byte[] getBytes() 
{
        int    size  = getSize();
        byte[] bytes = new byte[ size ];
        writeBytes(bytes, 0);
        return bytes;
}

 abstract public int getSize()

 abstract public String toFormulaString()

 abstract public  void writeBytes(byte[] array,
    int offset)