//UnknownOpException.java

public class UnknownOpException
    extends Exception
{
    public UnknownOpException()
    {
        super("UnknownOpException");
    }

    public UnknownOpException
    (
        char op
    )
    {
        super(op + " is an unknown operator.");
    }

    public UnknownOpException
    (
        String message
    )
    {
        super(message);
    }
}