Any thoughts on what the validator is looking for?

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Any thoughts on what the validator is looking for? As far as I can tell, I am meeting the requirements, but good ol' Mr. validator is not having it. I'm actually kind of impressed with my code here. Not that I think it is amazing code in the grand scheme of things, but just that it ended up being fairly clean and modular, which is an achievement for me lol. Any thoughts are much appreciated.

Implement the getPassword() method, which must return a ByteArrayOutputStream with the bytes comprising the password.
Password requirements:
1) 8 characters.
2) Only numbers and uppercase and lowercase Latin letters.
3) At least one numeral, one lowercase letter, and one uppercase letter.
All generated passwords must be unique.

Example of a valid password:
wMh7smNu

Requirements:

The Solution class must have a getPassword() method that returns a ByteArrayOutputStream with the generated password.
The password must be 8 characters long.
The password must have at least one numeral.
The password must have at least one lowercase Latin letter.
The password must have at least one uppercase Latin letter.
The password must not have characters other than numerals and uppercase and lowercase Latin letters.
Generated passwords must be unique.

package com.codegym.task.task32.task3204; import java.io.ByteArrayOutputStream; /* Password generator use random int generator to make a random password with proper ascii character codes. // check conditions, if fails, run again until it passes use multiple random number generators: 1: numeral 2: uppercase letter 3: lowercase letter a master random number generator that randomly calls one of the 3 character generators call it 8 times */ public class Solution { public static void main(String[] args) { ByteArrayOutputStream password = getPassword(); System.out.println(password.toString()); } public static ByteArrayOutputStream getPassword() { ByteArrayOutputStream out = new ByteArrayOutputStream(8); byte[] characters = randomArrayFiller(); boolean containsUpper = false; boolean containsLower = false; boolean containsNumeral = false; for (int i = 0; i < characters.length; i++) { if (characters[i] >= 48 && characters[i] <= 57) { containsNumeral = true; } else if (characters[i] >= 65 && characters[i] <= 90) { containsUpper = true; } else if (characters[i] >= 97 && characters[i] <= 122) { containsLower = true; } } if (containsNumeral && containsUpper && containsLower) { out.write(characters, 0, 8); return out; } else { getPassword(); } return null; } //TODO check the boundaries of the random functions to make sure they are getting the 1st and last characters correct; public static int getRandomNumeral() { int max = 57; int min = 48; int range = max - min + 1; int rand = 0; // generate random numeral for (int i = 0; i < max; i++) { rand = (int) (Math.random() * range) + min; } return rand; } public static int getRandomUppercase() { int max = 90; int min = 65; int range = max - min + 1; int rand = 0; // generate random uppercase letter for (int i = 0; i < max; i++) { rand = (int) (Math.random() * range) + min; } return rand; } public static int getRandomLowercase() { int max = 122; int min = 97; int range = max - min + 1; int rand = 0; // generate random lowercase letter for (int i = 0; i < max; i++) { rand = (int) (Math.random() * range) + min; } return rand; } public static int randomFunctionCaller() { int max = 3; int min = 1; int range = max - min + 1; int rand = 0; // generate random numbers to call functions at random for (int i = 0; i < max; i++) { rand = (int) (Math.random() * range) + min; } if (rand == 1) { return getRandomNumeral(); } else if (rand == 2) { return getRandomUppercase(); } else { return getRandomLowercase(); } } public static byte[] randomArrayFiller() { byte[] bytes = new byte[8]; for (int i = 0; i < 8; i++) { bytes[i] = (byte) randomFunctionCaller(); } return bytes; } }

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Guadalupe Gagnon

Level 37 , Tampa, United States

26 August 2020, 20:21

solution

This code can return null, it should not do that. It returned null on the 4th time running it for me. Fix it so that all paths lead to a valid output. When you make a recursive function, the line that calls the function is where the value will be and then the code will continue. Following the logic, if line 47 is reached it calls the getPassword() method again but no return value is saved, then the code will continue at line 49 and return null. Other than that I do agree that your code is clean and demonstrates good object orientated technique, to my understanding. You should be able to take my hint and fix your code quite easily so that it always returns a valid value.

Dave Andrea

Level 41 , Canada

26 August 2020, 21:02

Thank you so much Guadalupe!!! I ran it a few times last night and I got 4 or 5 good results in a row so I assumed it was all good. But of course, after reading your answer, 2 of the 3 times I ran the program it returned null lol. Yes, I was definitely misunderstanding recursion and I thought it would return the value of the recursive function call to the outer function, which would then return it to main. But it didn't, and it went on to return the null value as you explained. I thought the null value was unreachable (though the fact that intelliJ didn't give me a warning that it was unreachable should have made a lightbulb go off...).

Dave Andrea

Level 41 , Canada

26 August 2020, 21:08

If anyone in the future is interested in the fixed getPassword() method.

public static ByteArrayOutputStream getPassword() {
        ByteArrayOutputStream out = new ByteArrayOutputStream(8);
        byte[] characters = new byte[8];
        boolean containsUpper = false;
        boolean containsLower = false;
        boolean containsNumeral = false;

        while (!(containsNumeral && containsUpper && containsLower)) {
            containsUpper = false;
            containsLower = false;
            containsNumeral = false;
            characters = randomArrayFiller();
            for (int i = 0; i < characters.length; i++) {
                if (characters[i] >= 48 && characters[i] <= 57) {
                    containsNumeral = true;
                } else if (characters[i] >= 65 && characters[i] <= 90) {
                    containsUpper = true;
                } else if (characters[i] >= 97 && characters[i] <= 122) {
                    containsLower = true;
                }
            }
        }
        out.write(characters, 0, 8);
            return out;
        }

Guadalupe Gagnon

Level 37 , Tampa, United States

27 August 2020, 00:01

useful

So, your original code worked great other than the 1 recursive call. When I was testing your code, this was the solution I came up with to get it to work:

if (containsNumeral && containsUpper && containsLower)
   out.write(characters, 0, 8);
else
   out = getPassword();

return out;

Now, I should say that recursive methods generally should be avoided because they can be resource intensive. It would be very unlikely that this code would go down more than 2 levels total in recursive calls, but if it did for every time it would block out memory for each of the declared booleans, the ByteArrayOutputStream, and the byte[]. It is entirely possible to actually run out of memory using recursion. It is actually safer and less work on the CPU to solve this in a loop as you did with the conclusion that you came to. I personally think that a do-while loop would make more sense, not necessarily "better" though. This difference is that in a do while loop the condition is checked at the end instead of the beginning of the loop which guarantees that it will run at least once. This would be an example with relevant line changes:

byte[] characters;
boolean containsUpper;
boolean containsLower;
boolean containsNumeral;

do {
   containsUpper = false;
   containsLower = false;
   containsNumeral = false;
   characters = randomArrayFiller();

   for (int i = 0; i < characters.length; i++)
      if (characters[i] >= 48 && characters[i] <= 57)
         containsNumeral = true;
      else if (characters[i] >= 65 && characters[i] <= 90)
         containsUpper = true;
      else if (characters[i] >= 97 && characters[i] <= 122)
         containsLower = true;

}while (!(containsNumeral && containsUpper && containsLower));

Dave Andrea

Level 41 , Canada

27 August 2020, 01:52

Ok. The do-while loop also simplifies it a bit because then you don't have to initialize the variables before the loop. Generally, I hate recursion because it twists my mind in knots, so I'm glad to hear that loops are generally better. Much more intuitive to me.