return error if no subreddit is specified

src/main/java/sh/adb/RandomRedditMemesAPI/CommunityHandler.java

@@ -33,12 +33,32 @@ class CommunityHandler implements HttpHandler {
         subJSON.put("permalink", sub.getPermalink());
         return subJSON;
     }
+    private void sendResponse(HttpExchange t, String response) throws IOException {
+        System.out.println("response > "+response);
+        Headers headers = t.getResponseHeaders();
+        headers.set("Content-Type", "application/json; charset=UTF-8");
+        System.out.println(response.length());
+        OutputStream os = t.getResponseBody();
+        headers.add("Connection", "close");
+        t.sendResponseHeaders(200, response.length());
+        os.write(response.getBytes(StandardCharsets.UTF_8));
+        os.close();
+    }
 
     @Override
     public void handle(HttpExchange t) throws IOException {
         System.out.println("request at > "+t.getRequestURI().toString());
         String[] pathArray = t.getRequestURI().toString().split("/", -1);
 
+        JSONObject responseJSON = new JSONObject();
+        JSONArray subsJSON = new JSONArray();
+
+        if (pathArray.length < 5 || pathArray[4].equals("")){
+            responseJSON.put("error", "no subreddit specified");
+            sendResponse(t, responseJSON.toString());
+            return;
+        }
+
         List<Submission> submissions = null;
         try {
             submissions = this.api.getSub(pathArray[4]);
@@ -47,8 +67,6 @@ class CommunityHandler implements HttpHandler {
         }
         assert submissions != null;
 
-        JSONObject responseJSON = new JSONObject();
-        JSONArray subsJSON = new JSONArray();
         if ( pathArray.length < 6 || pathArray[5].equals("") || pathArray[5].equals("random")) {
             Random rand = new Random();
             subsJSON.put(subToJSON(
@@ -76,16 +94,6 @@ class CommunityHandler implements HttpHandler {
             }
         }
         responseJSON.put("subs", subsJSON);
-        
-        String response = responseJSON.toString();
-        System.out.println("response > "+response);
-        Headers headers = t.getResponseHeaders();
-        headers.set("Content-Type", "application/json; charset=UTF-8");
-        System.out.println(response.length());
-        OutputStream os = t.getResponseBody();
-        headers.add("Connection", "close");
-        t.sendResponseHeaders(200, response.length());
-        os.write(response.getBytes(StandardCharsets.UTF_8));
-        os.close();
+        sendResponse(t, responseJSON.toString());
     }
 }