Quick way to create an uppercase letter-only string from a long value.

Today I had to find a quick way to convert the current time in milliseconds into an uppercase letter-only ([A-Z]+) string with possibly minimal length. java.util.UUID did not seem to fit well to the purpose as it produces [0..9A..F]+ that requires extra conversion so I come up with the following:

public static String makeUppercaseLetterOnlyStringFromCurrentTime() {         final long ts = System.currentTimeMillis();         // convert the value to range of 0..9a...z characters         final String chars = Long.toString(ts, 26);         final StringBuilder sb = new StringBuilder();         for (byte b : chars.getBytes()) {             final int ch = (int) b;             // for a digit subtract '0' and add to 'A',              // for a letter - subtract 'a' and and add to 'A'             final int x = b + ((Character.isDigit(b)) ? 0x11 : -0x20);             sb.append((char) x);         }         return sb.toString();     }

This for sure is not the fastest nor the most efficient approach yet quite straight-forward one. :-)