I am writing a method and would like to start the method with a comparison to see if a stored static string is equal to other words. Here it is in psuedocode:
While (String1 is neither equal to "A" nor "B" nor "C" nor "D")
{
Print (Please enter a correct option);
Take input;
}
Any help is great thanks.
In your case, you have four admissible inputs namely "A", "B", "C", "D". This can easily be implemented only using boolean operators; namely the loop condition is when your input is neither that of "A" nor "B" nor "C" nor "D".
Scanner input = new Scanner(System.in);
System.out.println("Enter a selection (NOR): ");
String string1 = input.next();
while ( !string1.equals("A")
&& !string1.equals("B")
&& !string1.equals("C")
&& !string1.equals("D")) {
System.out.println("Enter again (NOR): ");
string1 = input.next();
}
input.close();
But what about situations where there are arbitrarily but finitely many admissible inputs, such as having all letters of the Hungarian alphabet? The set may be the best option.
Scanner input = new Scanner(System.in);
// Either manually or use a method to add admissible values to the set
Set<String> admissible = new HashSet<String>();
admissible.add("A");
admissible.add("B");
admissible.add("C");
admissible.add("D");
// ... and so on. You can also use helper methods to generate the list of admissibles
// in case if it is in a file (such as a dictionary or list of words).
System.out.println("Enter a selection (Set): ");
String string1 = input.next();
// If input string1 is not found anywhere in the set
while (!admissible.contains(string1)) {
System.out.println("Enter again (Set): ");
string1 = input.next();
}
input.close();
!string1.equals("A") && !string1.equals("B") && ... will be the most efficient for small number of elements. At some number the set will become better. I don't think regex will be the worst variant as it's essentially the same as !string1.equals("A") && !string1.equals("B") && ... but with some overhead.As Hemant stated in their comment, it'd be smart to use a Set to store whatever Strings you want to check against:
Set<String> words = Set.of("Hello", "World!");
while (!words.contains(string1)) {
...
}
Note: Set#of was introduced in Java 9, and string1 is the String that you're checking against.
// static set at top of the class
private static final Set<String> SET = new HashSet<>
(Arrays.asList("A", "B", "C", "D"));
void func() {
String input = takeInput();
while(!SET.contains(input)) {
input = takeInput();
}
}
set troubles me xD
SET.One approach is to construct a simple regular expression to match your strings:
String input = "";
while (!Pattern.matches("FirstString|SecondString|ThirdString", input)) {
...
}
Regular expression pattern is composed of the words that you wish to allow separated by the vertical bar | character.
Note: Using while loop requires setting input to a non-matching String before entering the loop. You can improve upon this by changing to do / while loop:
String input;
do {
System.out.println("Please enter a correct option");
input = takeInput();
} while (!Pattern.matches("FirstString|SecondString|ThirdString", input));
set.contains(string1)in while loopdo while loop