Added the code for url shortener using java

Author: nishthax

UrlShortener.java

@@ -0,0 +1,52 @@
+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);
+    }
+}