Read one char only from serial and clear buffer

Using Arduino Networking, Protocols, and Devices
6

You can simplify somewhat. This ignores line feed and return characters and prints the prompt on any but '0' or '1'

void loop() {
 	 if (Serial.available()) {
		char userCharacter = Serial.read();
		switch ( userCharacter ) {
			case ‘0’ : 
				controlBoiler ( 0 );
				break;
			case ‘1’ :
				controlBoiler ( 1 );
				break;
			case 10 : // Line feed
			case 13 : // carriage return
				break;
			default :       
				Serial.println("Please input 1 (ON) or 0 (OFF)”);
				break;
		}
	}
}