made minor changes

Author: huixianc

build.gradle

@@ -36,6 +36,21 @@ test {
 
 dependencies {
     testImplementation 'org.junit.jupiter:junit-jupiter:5.5.0'
+
+    String javaFxVersion = '11'
+
+    implementation group: 'org.openjfx', name: 'javafx-base', version: javaFxVersion, classifier: 'win'
+    implementation group: 'org.openjfx', name: 'javafx-base', version: javaFxVersion, classifier: 'mac'
+    implementation group: 'org.openjfx', name: 'javafx-base', version: javaFxVersion, classifier: 'linux'
+    implementation group: 'org.openjfx', name: 'javafx-controls', version: javaFxVersion, classifier: 'win'
+    implementation group: 'org.openjfx', name: 'javafx-controls', version: javaFxVersion, classifier: 'mac'
+    implementation group: 'org.openjfx', name: 'javafx-controls', version: javaFxVersion, classifier: 'linux'
+    implementation group: 'org.openjfx', name: 'javafx-fxml', version: javaFxVersion, classifier: 'win'
+    implementation group: 'org.openjfx', name: 'javafx-fxml', version: javaFxVersion, classifier: 'mac'
+    implementation group: 'org.openjfx', name: 'javafx-fxml', version: javaFxVersion, classifier: 'linux'
+    implementation group: 'org.openjfx', name: 'javafx-graphics', version: javaFxVersion, classifier: 'win'
+    implementation group: 'org.openjfx', name: 'javafx-graphics', version: javaFxVersion, classifier: 'mac'
+    implementation group: 'org.openjfx', name: 'javafx-graphics', version: javaFxVersion, classifier: 'linux'
 }
 
 application {

src/main/java/MainWindow.java

@@ -60,6 +60,7 @@ private void handleUserInput() {
             );
 
             Platform.exit();
+            System.exit(0);
         }
 
     }