kristofer / UrlShortener.java

import java.security.MessageDigest; import java.security.NoSuchAlgorithmException; import java.util.HashMap; import java.util.Map; import java.util.Random; public class UrlShortener { private Map<String, String> urlMap = new HashMap<>(); private static final String BASE_URL = "http://short.url/"; public String shortenUrl(String originalUrl) { String shortUrl = generateShortUrl(originalUrl); urlMap.put(shortUrl, originalUrl); return BASE_URL + shortUrl; } public String expandUrl(String shortUrl) { String shortKey = shortUrl.substring(BASE_URL.length()); return urlMap.get(shortKey); } private String generateShortUrl(String originalUrl) { try { MessageDigest md = MessageDigest.getInstance("MD5"); byte[] digest = md.digest(originalUrl.getBytes()); StringBuilder shortUrl = new StringBuilder(); Random random = new Random(); for (int i = 0; i < 6; i++) { int index = random.nextInt(digest.length); shortUrl.append(String.format("%02x", digest[index])); } return shortUrl.toString(); } catch (NoSuchAlgorithmException e) { e.printStackTrace(); return null; } } public static void main(String[] args) { UrlShortener urlShortener = new UrlShortener(); String longUrl = "https://www.example.com/some/long/url"; String shortUrl = urlShortener.shortenUrl(longUrl); System.out.println("Short URL: " + shortUrl); String expandedUrl = urlShortener.expandUrl(shortUrl); System.out.println("Expanded URL: " + expandedUrl); } }