Get error java cannot find symbol when I use "var" keyword with language level set to JDK 11

If I try compiling a Java 11 class using the var keyword I get a message saying: Error:(15, 13) java: cannot find symbol
symbol: class var
location: class ImageViewer

I am able to compile the class from the command line just fine.  Here is my code:

public class ImageViewer {
    public static void main(String[] args) {
        EventQueue.invokeLater(() -> {
            var frame = new ImageViewerFrame();
            frame.setTitle("ImageViewer");
            frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
            frame.setVisible(true);
        });
    }
}

/**
 * A frame with a label to show an image.
 */

class ImageViewerFrame extends JFrame {
    private static final int DEFAULT_WIDTH = 300;
    private static final int DEFAULT_HEIGHT = 400;

    public ImageViewerFrame() {
        setSize(DEFAULT_WIDTH, DEFAULT_HEIGHT);

        // Use a label to display the images
        var label = new JLabel();
        add(label);

        // Set up the file chooser
        var chooser = new JFileChooser();
        chooser.setCurrentDirectory(new File("."));

        // Set up the menu bar
        var menuBar = new JMenuBar();
        setJMenuBar(menuBar);

        var menu = new JMenu("File");
        menuBar.add(menu);

        var openItem = new JMenuItem("Open");
        menu.add(openItem);
        openItem.addActionListener(event -> {
            // Show file chooser dialog
            int result = chooser.showOpenDialog(null);

            // If file selected, set it as icon of the label
            if (result == JFileChooser.APPROVE_OPTION) {
                String name = chooser.getSelectedFile().getPath();
                label.setIcon(new ImageIcon(name));
            }
        });

        var exitItem = new JMenuItem("Exit");
        menu.add(exitItem);
        exitItem.addActionListener(event -> System.exit(0));
    }