By using UUID is it possible to generate a 16 character String?

Another best option by using Apache commons

import org.apache.commons.lang3.RandomStringUtils;
RandomStringUtils.randomAlphanumeric(10);

above code will generate a random string. output: ZBgTxJX93f

Reference : https://www.mkyong.com/java/java-how-to-generate-a-random-string/

A GUID / UUID is a 128 bit number often represented as a series of 32 HEX values. A HEX value is base 16. If you want to represent the same 128bit value in 16 digits then you'll need to use base 64 digits.

To do that you'll need to create a mapping similar to how HEX values are mapped. The English alphabet has 26 characters and ASCII has a value for them in both upper and lower case. This gives us 52 distinct digits. Add to that the numerical values 0 to 9 and that brings us to 62. Then you can pick whatever to get you to 64, say '*' and '+', or whatever makes the most sense taking into account their position in the ASCII table. So then you'd create a lookup table that translates between these 64 digits to build a 128 bit value.

This should give you a full 128bit value represented in 16 Base-64 characters. It would look something like: GaUvr*olp42xgtyu

Note that this is not standard and you'd need to control both the encoder and decoder.