public static String random(final int count, final boolean letters, final boolean numbers) {
        return random(count, 0, 0, letters, numbers);
    }
<p>Creates a random string whose length is the number of characters
specified.</p>

<p>Characters will be chosen from the set of alpha-numeric
characters as indicated by the arguments.</p>

@param count   the length of random string to create
@param letters if {@code true}, generated string may include
               alphabetic characters
@param numbers if {@code true}, generated string may include
               numeric characters
@return the random string
android/android_framework/base/src/main/java/lang3/RandomStringUtils.java