Introduction to Java Programming编程题9.1<检查SSN>

/*
Enter your SSN: 123-45-666666
Invalid SSN.
Enter your SSN: okl-33-4444
Invalid SSN.
Enter your SSN: 123-45-6789
Valid SSN
*/
import java.util.Scanner;

public class CheckSSN {
public static void main(String[] args) {
Scanner input = new Scanner(System.in);

System.out.print("Enter your SSN: ");
String SSN = input.nextLine();

final int SIZE = 11;
for (int i = 0; i < SIZE; i++) {
if (SIZE != SSN.length() || !Character.isDigit(SSN.charAt(i))) {
if (i == 3 || i == 6) {
if (SSN.charAt(i) == '-' || SSN.charAt(i) == '-')
continue;
}
System.out.println("Invalid SSN.");
System.exit(0);
}
}
System.out.println("Valid SSN");
}
}