Program to Check if a String contains only digits?

public class CheckDigits {
public static void main(String[] args) {
String s = “12345”;
boolean flag = true;
for(int i=0; i<s.length(); i++) {
if(!Character.isDigit(s.charAt(i))) {
flag = false;
break;
}
}
System.out.println(flag);
}
}

Output: