input character inside a while loop with validation

System.out.print("Enter the operator (+ - X /): ");
operator = input.next();
char c=operator.charAt(0);
while (c != '+' && c != '-' && c != '*' && c != '/')
System.out.println("Operator doesn't match. Try again.");
System.out.print("Enter the operator (+ - X /): ");
input.next().charAt(0);



Here, I want an input character value from keyboard which will be only symbols just (+ - * /) inside a while loop. if the sign is not match the while loop will be running.

while

Here, the while loop is working but the character is not checked. So, while loop continuously works with-

while

System.out.println("Operator doesn't match. Try again.");
System.out.print("Enter the operator (+ - X /): ");


2 Answers
2

You call a blank call to input.next().charAt(0); but this does nothing but read the next character. c is never changed so it always will be the invalid input. You need to resolve it back to c:

input.next().charAt(0);

c

c

c = input.next().charAt(0);


In the last line of your while loop, you are retrieving an user input, but not storing it anywhere. You should do like that:

c = input.next().charAt(0);


If you want to do something fancy, you could also try using the do-while loop, like below:

char c;
do
System.out.println("Enter a operator (+ - * /):");
c = input.next().charAt(0);
while(c != '+' && c != '-' && c != '*' && c != '/');


By clicking "Post Your Answer", you acknowledge that you have read our updated terms of service, privacy policy and cookie policy, and that your continued use of the website is subject to these policies.