docs: update promise

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

@@ -78,7 +78,6 @@ public class App {
    *
    * @param args arguments
    * @throws InterruptedException if main thread is interrupted.
-   * @throws ExecutionException   if an execution error occurs.
    */
   public static void main(String[] args) throws InterruptedException {
     var app = new App();
@@ -123,7 +122,7 @@ public class App {
 
   /*
    * Calculate the character frequency of a file and when that promise is fulfilled,
-   * then promise to apply function to calculate lowest character frequency.
+   * then promise to apply function to calculate the lowest character frequency.
    */
   private Promise<Character> lowestFrequencyChar() {
     return characterFrequency().thenApply(Utility::lowestFrequencyChar);
@@ -155,7 +154,7 @@ public class App {
             () -> Utility.downloadFile(urlString), executor)
         .onError(
             throwable -> {
-              throwable.printStackTrace();
+              LOGGER.error("An error occurred: ", throwable);
               taskCompleted();
             }
         );

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

@@ -45,7 +45,7 @@ public class Promise<T> extends PromiseSupport<T> {
   private Consumer<? super Throwable> exceptionHandler;
 
   /**
-   * Creates a promise that will be fulfilled in future.
+   * Creates a promise that will be fulfilled in the future.
    */
   public Promise() {
     // Empty constructor

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

@@ -58,7 +58,7 @@ public class Utility {
           .mapToObj(x -> (char) x)
           .collect(Collectors.groupingBy(Function.identity(), Collectors.counting()));
     } catch (IOException ex) {
-      ex.printStackTrace();
+      LOGGER.error("An error occurred: ", ex);
     }
     return Collections.emptyMap();
   }
@@ -86,7 +86,7 @@ public class Utility {
     try (var bufferedReader = new BufferedReader(new FileReader(fileLocation))) {
       return (int) bufferedReader.lines().count();
     } catch (IOException ex) {
-      ex.printStackTrace();
+      LOGGER.error("An error occurred: ", ex);
     }
     return 0;
   }

promise/src/test/java/com/iluwatar/promise/AppTest.java

@@ -24,11 +24,10 @@
  */
 package com.iluwatar.promise;
 
-import java.util.concurrent.ExecutionException;
-import org.junit.jupiter.api.Test;
-
 import static org.junit.jupiter.api.Assertions.assertDoesNotThrow;
 
+import org.junit.jupiter.api.Test;
+
 /**
  * Application test.
  */