Java 短链接生成算法

UrlShortener.java

public class UrlShortener {
//    private static final String ALPHABET = "abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789";
    private static final String ALPHABET = "mUSNcOa6hDgfnEJ1rGMPC03jv4k9RIqL2Yy7TQdH8xu5XFWwAKoZVstizlepBb";
    private static final int    BASE     = ALPHABET.length();

    public static String encode(int num) {
        StringBuilder sb = new StringBuilder();
        while (num > 0) {
            sb.append(ALPHABET.charAt(num % BASE));
            num /= BASE;
        }
        return sb.reverse().toString();
    }

    public static int decode(String str) {
        int num = 0;
        for (int i = 0; i < str.length(); i++)
            num = num * BASE + ALPHABET.indexOf(str.charAt(i));
        return num;
    }

    public static void main(String[] args) {
        for (int i = 14776336; i < 14877336; i++) {
            System.out.println(encode(i));
        }
    }
}