1: 2: public class UnknownOpException extends Exception 3: { 4: public UnknownOpException( ) 5: { 6: super("UnknownOpException"); 7: } 8: public UnknownOpException(char op) 9: { 10: super(op + " is an unknown operator."); 11: } 12: public UnknownOpException(String message) 13: { 14: super(message); 15: } 16: }