do-while loopwith 3 conditions

Question

I'm in a stuck with do-while looping that requires looping with do-while until users input one of three correct strings

I've tried with this

Scanner input = new Scanner(System.in);
    String motor = "motor";
    String mobil = "mobil";
    String kosong = "";
    String baru = "baru";
    int tahun = Calendar.getInstance().get(Calendar.YEAR);

do {
        inputVehicleType();
        vehicleCondition = input.next();
    }
while (!(vehicleCondition.equals(motor)) || (vehicleCondition.equals(mobil)) || (vehicleCondition.equals(kosong)));

System.out.println("SUCCED");

private static void inputVehicleType() {
    System.out.println(Constant.HEADER);
    System.out.println("Input Jenis Kendaraan Mobil/Motor --> (jenis [motor/mobil])");
    titleFooter();
}

with that syntax it only retrieve (vehicleCondition.equals(motor). My expected result was it can retrieve (vehicleCondition.equals(motor), (vehicleCondition.equals(mobil), (vehicleCondition.equals(kosong).

score 5 · Accepted Answer · answered Jun 27 '19 at 07:25

If you remove the excess parentheses it may be easier to spot that you have while (!a || b || c) instead of while (!(a || b || c)).

do {
    ...
} while (!(vehicleCondition.equals(motor) ||
           vehicleCondition.equals(mobil) ||
           vehicleCondition.equals(kosong)));

Or, equivalently via De Morgan's laws, while (!a && !b && !c):

do {
    ...
} while (!vehicleCondition.equals(motor) &&
         !vehicleCondition.equals(mobil) &&
         !vehicleCondition.equals(kosong));

score 3 · Answer 2 · answered Jun 27 '19 at 07:28

3

You have made a mistake in your while logic expression

should be:

while (!((vehicleCondition.equals(motor)) || (vehicleCondition.equals(mobil)) || (vehicleCondition.equals(kosong))));

answered Jun 27 '19 at 07:28

PrzemyslawP

190
1
13

score 1 · Answer 3 · answered Jun 27 '19 at 07:25

The correct condition would be:

while (!(vehicleCondition.equals(motor) || 
         vehicleCondition.equals(mobil) || 
         vehicleCondition.equals(kosong)));

i.e. you should stay in the loop as long as vehicleCondition is not equal to one of the 3 expected values.

Bentaye · Answer 4 · 2019-06-27T07:47:03.607

0

Make a method to check the condition:

private static boolean isValidVehiculeCondition(String vc) {
    return !Arrays.asList("motor", "mobil", "baru").contains(vc.toLowerCase());
}

Then loop while it returns true (ie: input is not valid)

do {
    inputVehicleType();
} while(isNotValidVehiculeCondition(input.next()));

edited Jun 27 '19 at 07:47

answered Jun 27 '19 at 07:31

Bentaye

9,403
5
32
45

score 0 · Answer 5 · answered Jun 27 '19 at 07:35

I think you have a little parenthesis mistake in your code. You need to add an extra parenthesis around not operator. Your condition should be

while (!(
  (vehicleCondition.equals(motor)) ||
  (vehicleCondition.equals(mobil)) || (vehicleCondition.equals(kosong))
));

do-while loopwith 3 conditions

5 Answers5