Fix codebase based off code quality feedback

- Task.java: Naming of boolean variable
- Duke.java: Fix header of javadocs
- Ui.java: Fix header of javadocs

src/main/java/duke/main/Duke.java

@@ -31,8 +31,10 @@ public Duke() {
     }
 
     /**
-     * You should have your own function to generate a response to user input.
-     * Replace this stub with your completed method.
+     * Generates a response to user input.
+     *
+     * @param input input is the user input keyed into the input field.
+     * @return Returns the response from the system back to the user.
      */
     public String getResponse(String input) {
         assert input != null : "Duke[getResponse] input cannot be null.";

src/main/java/duke/ui/Ui.java

@@ -38,7 +38,7 @@ public void output(String output) {
     }
 
     /**
-     * Display a message when there is an issue loading from the text file that holds tasks.
+     * Displays a message when there is an issue loading from the text file that holds tasks.
      */
     public void showLoadingError() {
         output(Constants.STORAGE_READ_MSG);