public class Codec {    private long id;    private Map
     
       urlMap;    private final String elements = "0123456789abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ";        public Codec() {        id = 0L;        urlMap = new HashMap<>();    }    // Encodes a URL to a shortened URL.    public String encode(String longUrl) {        urlMap.put(id, longUrl);        return encode(id++);    }        private String encode(long id) {        StringBuilder result = new StringBuilder();        while (id > 0) {            result.append(elements.charAt((int)(id % 62)));            id /= 62;        }        return result.toString();    }    // Decodes a shortened URL to its original URL.    public String decode(String shortUrl) {        return urlMap.get(mapTo(shortUrl));    }        private long mapTo(String url) {        long result = 0;        for (int i = url.length() - 1; i >= 0; i--) {            result += maps(url.charAt(i)) * Math.pow(62, (url.length() - i - 1));        }        return result;    }        private int maps(char c) {        if (c >= '0' && c <= '9') {            return Integer.valueOf(c);        } else if (c >= 'a' && c <= 'z') {            return 10 + (int)(c - 'a');        } else if ( c >= 'A' && c <= 'Z') {            return 36 + (int)(c - 'A');        }        return 0;    }}// Your Codec object will be instantiated and called as such:// Codec codec = new Codec();// codec.decode(codec.encode(url));