Minor refactorings and code style changes (#807)

* Made minor changes in some patterns such as removed throws clause where not needed, changed incorrect order of arguments in assertEquals

* Minor refactorings and code style changes. 1) Removed several use of raw types 2) Removed unnecessary throws clauses 3) Used lambda expressions wherever applicable 4) Used apt assertion methods for readability 5) Use of try with resources wherever applicable 6) Corrected incorrect order of assertXXX arguments

* Removed unused import from Promise

* Addressed review comments

* Addressed checkstyle issue

promise/src/main/java/com/iluwatar/promise/App.java

@@ -155,19 +155,15 @@ public class App {
    * This is an async method and does not wait until the file is downloaded.
    */
   private Promise<String> download(String urlString) {
-    Promise<String> downloadPromise = new Promise<String>()
+    return new Promise<String>()
         .fulfillInAsync(
-            () -> {
-              return Utility.downloadFile(urlString);
-            }, executor)
+            () -> Utility.downloadFile(urlString), executor)
         .onError(
             throwable -> {
               throwable.printStackTrace();
               taskCompleted();
             }
         );
-
-    return downloadPromise;
   }
 
   private void stop() throws InterruptedException {

promise/src/main/java/com/iluwatar/promise/Utility.java

@@ -32,7 +32,6 @@ import java.io.FileWriter;
 import java.io.IOException;
 import java.io.InputStreamReader;
 import java.io.Reader;
-import java.net.MalformedURLException;
 import java.net.URL;
 import java.util.HashMap;
 import java.util.Iterator;
@@ -111,7 +110,7 @@ public class Utility {
    * Downloads the contents from the given urlString, and stores it in a temporary directory.
    * @return the absolute path of the file downloaded.
    */
-  public static String downloadFile(String urlString) throws MalformedURLException, IOException {
+  public static String downloadFile(String urlString) throws IOException {
     LOGGER.info("Downloading contents from url: {}", urlString);
     URL url = new URL(urlString);
     File file = File.createTempFile("promise_pattern", null);