Poechant 練習 Java API - Y/N 輸入驗證

import java.util.Scanner;

public class test {
	public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);
		boolean isValid = false;
		while (!isValid) {
			String str = sc.next(); 
			if (str.equalsIgnoreCase("y")) {
				System.out.println("YES");
				isValid = true;
			} else if (str.equalsIgnoreCase("n")) {
				System.out.println("NO");
				isValid = true;
			} else {
				System.out.println("Please input \"y\" or \"n\"");
			}
		}
	}
}