public final class URLGenerator
extends java.lang.Object
ShortURL: Bijective conversion between natural numbers (IDs) and short
strings
ShortURL.encode() takes an ID and turns it into a short string
ShortURL.decode() takes a short string and turns it into an ID
Features: + large alphabet (51 chars) and thus very short resulting strings +
proof against offensive words (removed 'a', 'e', 'i', 'o' and 'u') +
unambiguous (removed 'I', 'l', '1', 'O' and '0')
Example output: 123456789 <=> pgK8p
保证双射即可，基本不调用decode。