Not recognizing isDigit and isLetter char commands

When I run through the code is won't get past checking if there is a letter or digit. It just keeps asking for it, and not sure how to fix it. This is for a homework assignment.
Thank you for your time.

import java.util.Scanner;
public class Password {
	public static void main (String args[]) {
		Scanner inputDevice = new Scanner(System.in);
		String password;
		String password2;
		int length;
		char aChar;
		boolean success = false;
		boolean match = false;
		
		while (!success) {
			System.out.println("Please enter a password");
			password = inputDevice.nextLine();
			length = password.length();
			aChar = password.charAt(length-1);
			
			
			if (length >5 && length <10)  {
				if (Character.isDigit(aChar)) {
					if (Character.isLetter(aChar)) {
						System.out.println("This is a good password");
						success = true;
						while (!match) {
							System.out.println("Please retype password to confirm");
							password2 = inputDevice.nextLine();
							
							if (password.equals(password2)) {
								System.out.println("Your password matches");
								match = true;
							} else
								System.out.println("Your password did not match");
						}
					}else
						System.out.println("Password must contain a letter.");
				}else
					System.out.println("Password must contain a number.");
			} else 
					System.out.println("Password must be between 6 and 10 numbers and/or digits, and must contain 1 of each.");
		}
	}
}