How to generate a secure random alphanumeric string in Java efficiently?

Question

How do you generate a secure random (or pseudo-random) alphanumeric string in Java efficiently?

Answer 1

    String chrs = "0123456789abcdefghijklmnopqrstuvwxyz-_ABCDEFGHIJKLMNOPQRSTUVWXYZ";
    SecureRandom secureRandom = SecureRandom.getInstanceStrong();
    // 9 is the length of the string you want
    String customTag = secureRandom.ints(9, 0, chrs.length()).mapToObj(i -> chrs.charAt(i))
      .collect(StringBuilder::new, StringBuilder::append, StringBuilder::append).toString();
    System.out.println(customTag);

Examples:

// q3HX6EctP
// WjRrMjQT4
// sX-Piq4DB