Something

    public static Date getValidDate() throws IOException {
	 	Date tdate = new Date();
	 	int year, month, day;
	 	year= getValidYear();
	 	month = getValidMonth();
	 	day = getValidDay();
	 	tdate.setDate(day);
	 	tdate.setMonth(month);
	 	tdate.setYear(year);
	   	return tdate;
	}

    public static void addEntry(Vehicle [] vehicles, int counter) throws IOException{
		long kmtrage;
		vehicles[counter+1].setTdate(getValidDate()) ;
        }

java.lang.NullPointerException
    at controlVehicular.addEntry(controlVehicular.java:552)
    at controlVehicular.addSearchEntry(controlVehicular.java:661) :<