Simple Java Password Generator

PasswordGenerator.java

import java.security.SecureRandom;
import java.util.Arrays;
import java.util.Collections;
import java.util.List;

public class PasswordGenerator {

  // Cryptographically strong random number generator
  final SecureRandom random = new SecureRandom();

  // Min password length
  private static final int MIN_PASSWORD_LENGTH = 12;

  // Required password chars
  private static final char[][] passwordChars = {
      // Uppercase chars
      {'A', 'B', 'C', 'D', 'E', 'F', 'G', 'H', 'I', 'J', 'K', 'L', 'M', 'N', 'O', 'P', 'Q', 'R',
          'S', 'T', 'U', 'V', 'W', 'X', 'Y', 'Z'},
      // Lowercase chars
      {'a', 'b', 'c', 'd', 'e', 'f', 'g', 'h', 'i', 'j', 'k', 'l', 'm', 'n', 'o', 'p', 'q', 'r',
          's', 't', 'u', 'v', 'w', 'x', 'y', 'z'},
      // Digits
      {'0', '1', '2', '3', '4', '5', '6', '7', '8', '9'},
      // Special chars
      {'!', '@', '#', '$', '%', '^', '&', '*'},
  };

  public String generateRandomPassword() {
    // Password string builder
    final StringBuilder passwordBuilder = new StringBuilder();

    // First append password with required chars
    for (char[] chars : passwordChars) {
      passwordBuilder.append(chars[random.nextInt(chars.length)]);
    }

    // Calculate how many character we need to add for a secure password
    final int charsRemaining = MIN_PASSWORD_LENGTH - passwordBuilder.length();

    for (int i = 0; i < charsRemaining; i++) {
      // Choose a random password char arr
      char[] chars = passwordChars[random.nextInt(passwordChars.length)];

      // Append a random char
      passwordBuilder.append(chars[random.nextInt(chars.length)]);
    }

    // Shuffle password
    return shuffleString(passwordBuilder.toString());
  }

  // Shuffle string
  private static String shuffleString(String str) {
    List<String> stringList = Arrays.asList(str.split(""));
    Collections.shuffle(stringList);
    return String.join("", stringList);
  }

  public static void main(String[] args) {
    PasswordGenerator passwordGenerator = new PasswordGenerator();
    System.out.println(passwordGenerator.generateRandomPassword());
  }
}