Base62 | Base62 encoder/decoder for Java | Messaging library

I'm reading an online document that explains how to design a url shortening service. The website is https://www.educative.io/courses/grokking-the-system-design-interview .

In the section, Encoding actual URL, they said -> "We can compute a unique hash (e.g., MD5 or SHA256, etc.) of the given URL. The hash can then be encoded for displaying. This encoding could be base36 ([a-z ,0-9]) or base62 ([A-Z, a-z, 0-9]) and if we add ‘+’ and ‘/’ we can use Base64 encoding. A reasonable question would be, what should be the length of the short key? 6, 8, or 10 characters."

"If we use the MD5 algorithm as our hash function, it’ll produce a 128-bit hash value. After base64 encoding, we’ll get a string having more than 21 characters (since each base64 character encodes 6 bits of the hash value).Since we only have space for 8 characters per short key, how will we choose our key then? We can take the first 6 (or 8) letters for the key. This could result in key duplication, to resolve that, we can choose some other characters out of the encoding string or swap some characters."

I used online MD5 hash generator (http://onlinemd5.com/) and Base64 encoder (https://www.base64encode.org/) to verify the above. I used "www.yahoo.com" as the input string for MD5 hash and output is 1B03577ED104F16AADC00A639D33CB44 . Then I Base64 encoded it and got MUIwMzU3N0VEMTA0RjE2QUFEQzAwQTYzOUQzM0NCNDQ= with UTF-8 destination charset and Unix newline seperator.

Can anyone explain if I'm doing it correctly? I see the number of characters are way more than 21.

I want to encrypt and decrypt recursively any key which ends with id or _id.

It should loop through all the key inside passed array or object or array of objects to search for the key and encrypt it. Finally it will return encrypted data.

I tried below function, but it's not working.