Corrected files in order to pass checkstyle

build.gradle

@@ -8,8 +8,6 @@ plugins {
 group 'fr.univ_amu'
 version '1.0-SNAPSHOT'
 
-
-
 checkstyle {
     toolVersion = '10.3.4'
 }
@@ -19,14 +17,11 @@ repositories {
 }
 
 dependencies {
-    checkstyle "com.puppycrawl.tools:checkstyle:10.3.4"
     testImplementation('org.junit.jupiter:junit-jupiter-api:5.9.0',
             'org.assertj:assertj-core:3.23.1')
     testRuntimeOnly 'org.junit.jupiter:junit-jupiter-engine:5.9.0'
 }
 
-
-
 test {
     finalizedBy jacocoTestReport // report is always generated after tests run
 }
@@ -34,8 +29,6 @@ jacocoTestReport {
     dependsOn test // tests are required to run before generating the report
 }
 
-
-
 test {
     useJUnitPlatform()
 }

src/main/java/sample/MyJFrame.java → src/main/java/sample/MyJavaFrame.java

 package sample;
 
-import javax.swing.*;
-//import java.awt.*;
+import javax.swing.JFrame;
 
-public class MyJFrame extends JFrame{
-  public MyJFrame(){
+/**
+ * An extended version of javax.swing.JFrame containing a panel to draw images.
+ */
+public class MyJavaFrame extends JFrame {
+  /**
+   * Constructs a new visible frame.
+   */
+  public MyJavaFrame() {
     setTitle("Main window");
     setSize(400, 400);
     setLocationRelativeTo(null);
     setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
-    add(new MyJPanel());
+    add(new MyJavaPanel());
     setVisible(true);
   }
 
   public static void main(String[] args) {
-    MyJFrame app = new MyJFrame();
+    new MyJavaFrame();
   }
 }

src/main/java/sample/MyJPanel.java → src/main/java/sample/MyJavaPanel.java

 package sample;
 
-import javax.imageio.ImageIO;
-import javax.swing.*;
-import java.awt.*;
+import java.awt.Graphics;
 import java.awt.image.BufferedImage;
 import java.io.IOException;
+import java.util.Objects;
+import javax.imageio.ImageIO;
+import javax.swing.JPanel;
 
 
-public class MyJPanel extends JPanel {
+/**
+ * An extension of javax.swing.JFrame that can draw images.
+ */
+public class MyJavaPanel extends JPanel {
 
   private BufferedImage image;
+  /**
+   * Constructs a new panel that draw an image.
+   */
 
-  public MyJPanel() {
+  public MyJavaPanel() {
     try {
-      image = ImageIO.read(getClass().getResource("image.png"));
+      image = ImageIO.read(Objects.requireNonNull(getClass().getResource("image.png")));
     } catch (IOException ex) {
       System.out.println("problem! image can't be loaded!");
     }