[FIXED] Toolkit.getImage(URL url) works with Java 8 but fails with Java 11

Issue

I'm having a problem with a Java SE Swing application. It compiles fine on both Java 8 and 11, but it fails on the latter in these lines:

    URL url = Object.class.getResource("/org/mozillatranslator/resource/mt_icon_small.gif");
    Toolkit tk = Toolkit.getDefaultToolkit();

    Image img = tk.getImage(url); // Raises runtime exception

with this exception:

Caused by: java.lang.NullPointerException
    at java.desktop/sun.awt.SunToolkit.getImageFromHash(SunToolkit.java:653)
    at java.desktop/sun.awt.SunToolkit.getImage(SunToolkit.java:689)
    at org.mozillatranslator.gui.MainWindow.loadIcon(MainWindow.java:232)

As I've said, the line works on Java 8, but fails on Java 11 with the exact same JAR. I've searched for a change in Java behavior in versions beyond 8, but I haven't found anything. Has anyone suffered a similar situation, or can suggest any possible workarounds?

Solution

Use

URL url = <YourClassName>.class.getResource("/org/mozillatranslator/resource/mt_icon_small.gif");

or

URL url = Thread.currentThread()
    .getContextClassLoader()
    .getResource("org/mozillatranslator/resource/mt_icon_small.gif");

Object is loaded by bootstrap class loader, so Object.class.getResource() uses system class loader.

Check return values with empty string parameter; Object.class.getResource(""), YourClass.class.getResource(""), and Thread.currentThread().getContextClassLoader().getResource("").

Answered By - DEWA Kazuyuki - 出羽和之
Answer Checked By - Pedro (JavaFixing Volunteer)