diff --git a/src/main/java/duke/Duke.java b/src/main/java/duke/Duke.java
index cd902f9ccf..dcc3806e6c 100644
--- a/src/main/java/duke/Duke.java
+++ b/src/main/java/duke/Duke.java
@@ -1,8 +1,6 @@
 package duke;
 
-import duke.gui.MainWindow;
 import duke.task.TaskList;
-import javafx.scene.layout.AnchorPane;
 import javafx.stage.Stage;
 
 import java.io.FileNotFoundException;
@@ -12,12 +10,12 @@
  * Represents an intelligent chat robot that helps a person to keep track of various things with encouraging quotes.
  */
 public class Duke {
+    private static final String SAVING_ERROR_MSG = "⚠ Oops! Something wrong when closing:(";
+    private static final String BYE_MSG = "Bye!\n\"Beware the barrenness of a busy life.\"";
     private Parser parser;
     private Storage storage;
     private TaskList tasks;
     private Stage stage;
-    public String SAVING_ERROR_MSG = "⚠ Oops! Something wrong when closing:(";
-    public String BYE_MSG = "Bye!\n\"Beware the barrenness of a busy life.\"";
 
     /**
      * Initializes the chat robot. Establishes task list and parser.
@@ -50,7 +48,7 @@ public String getResponse(String input) {
         }
     }
 
-    public void close(){
+    public void close() {
         this.stage.close();
     }
 
diff --git a/src/main/java/duke/gui/MainWindow.java b/src/main/java/duke/gui/MainWindow.java
index 273a3afcbe..c79e0616d0 100644
--- a/src/main/java/duke/gui/MainWindow.java
+++ b/src/main/java/duke/gui/MainWindow.java
@@ -15,6 +15,9 @@
  * Controller for MainWindow. Provides the layout for the other controls.
  */
 public class MainWindow extends AnchorPane {
+    private static final String WELCOME_MSG = "Hi! This is your intelligent friend L.\n\"Dream big.\"\n"
+            + "What can I do for you today?";
+    private static final String BYE_MSG = "Bye!\n\"Beware the barrenness of a busy life.\"";
     @FXML
     private ScrollPane scrollPane;
     @FXML
@@ -26,9 +29,10 @@ public class MainWindow extends AnchorPane {
     private Duke duke;
     private Image userImage = new Image(this.getClass().getResourceAsStream("/images/DaUser.jpg"));
     private Image dukeImage = new Image(this.getClass().getResourceAsStream("/images/DaDuke.jpg"));
-    private String WELCOME_MSG = "Hi! This is your intelligent friend L.\n\"Dream big.\"\n"
-            + "What can I do for you today?";
 
+    /**
+     * Initializes the main window.
+     */
     @FXML
     public void initialize() {
         scrollPane.vvalueProperty().bind(dialogContainer.heightProperty());
@@ -54,7 +58,7 @@ private void handleUserInput() {
                 DialogBox.getDukeDialog(response, dukeImage)
         );
         userInput.clear();
-        if (response.equals(duke.BYE_MSG)){
+        if (response.equals(BYE_MSG)) {
             // Close the window after 5 seconds
             PauseTransition pause = new PauseTransition(Duration.seconds(5));
             pause.setOnFinished(event -> duke.close());
diff --git a/src/test/java/duke/ParserTest.java b/src/test/java/duke/ParserTest.java
index 4019dc540e..113310f111 100644
--- a/src/test/java/duke/ParserTest.java
+++ b/src/test/java/duke/ParserTest.java
@@ -8,13 +8,14 @@
 public class ParserTest {
 
     @Test
-    public void parse_bye_success() throws DukeException{
+    public void parse_bye_success() throws DukeException {
         assertEquals("", new Parser(null).parse("88"));
     }
     @Test
     public void parse_undefinedInput_exceptionThrown() {
-        try{
-            assertEquals("⚠ Sorry! I am not able to understand you. Try another language:D", new Parser(null).parse("undefined"));
+        try {
+            assertEquals("⚠ Sorry! I am not able to understand you. Try another language:D",
+                    new Parser(null).parse("undefined"));
             fail();
         } catch (DukeException e) {
             assertEquals("undefined", e.getMessage());
diff --git a/src/test/java/duke/task/TaskListTest.java b/src/test/java/duke/task/TaskListTest.java
index 55e3711121..e611900cf3 100644
--- a/src/test/java/duke/task/TaskListTest.java
+++ b/src/test/java/duke/task/TaskListTest.java
@@ -10,7 +10,7 @@ public class TaskListTest {
     @Test
     public void markTask_negativeIndex_exceptionThrown() {
         try {
-            assertEquals("⚠ OOPS!!! The task index is out of range.", new TaskList().markTask(-1,true));
+            assertEquals("⚠ OOPS!!! The task index is out of range.", new TaskList().markTask(-1, true));
             fail();
         } catch (Exception e) {
             assertEquals("task not found", e.getMessage());