Method java.awt.Toolkit.addPropertyChangeListener() says:

    /**
     ...
     * If {@code name} is {@code null} or {@code pcl} is {@code null},
     * no exception is thrown and no action is performed.
     ...
     */
    public void addPropertyChangeListener(String name, PropertyChangeListener pcl)

The assertion about null name is not satisfied by Windows/XToolkits.


The following code sample:
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import java.awt.*;
import java.beans.*;

public class AddPCL_NPE {
    public static void main(String[] args) {
        Toolkit.getDefaultToolkit().addPropertyChangeListener(null, new PropertyChangeListener() {
            @Override
            public void propertyChange(PropertyChangeEvent evt) { }
        });
    }
}

--------------------------------------------------------------------------------------------------

will produce output like:

Exception in thread "main" java.lang.NullPointerException
at sun.awt.windows.WDesktopProperties.isWindowsProperty(WDesktopProperties.java:77)
at sun.awt.windows.WToolkit.addPropertyChangeListener(WToolkit.java:882)

or

java.lang.NullPointerException
at sun.awt.X11.XToolkit.initXSettingsIfNeeded(XToolkit.java:1546)
at sun.awt.X11.XToolkit.addPropertyChangeListener(XToolkit.java:1535)