String-Conditionals in a Java While Loop

Question

I\'m trying to prompt the user to give me one of three strings: \"Amsterdam,\" \"Lexington,\" and \"Madison.\" If the user doesn\'t enter one of those strings, they should be re

Answer 1

If you use Java 7 or above I would prefer the following code:

public String readCity() {
    while (true) {
        String x = keyboard.next();

        switch(x) {
            case "Amsterdam":
            case "Lexington":
            case "Madison":
                return x;
            default:
                System.out.println("Please enter a valid city.");
         }
    }
}

Answer 2

You should use AND instead of OR like this:

String x = keyboard.next();
while (!x.equals("Amsterdam") && !x.equals("Lexington") && !x.equals("Madison")) {
    System.out.println("Please enter a valid city.");
    x = keyboard.next();
}

Answer 3

Refer to De-Morgan's laws:

(NOT a) OR (NOT b)

is actually

NOT (a AND b)

You need to have && instead of ||.