How to Create a Drop-Down Menu in a Java Swing Toolbar

How can I create a 'Drop-Down' menu in a Java Swing toolbar?

JComboBox comboBox = new JComboBox(); // Create a ComboBox
comboBox.addItem("Option 1"); // Add options
comboBox.addItem("Option 2");
comboBox.addItem("Option 3");
JToolBar toolBar = new JToolBar(); // Create the toolbar
toolBar.add(comboBox); // Add ComboBox to toolbar

Creating a drop-down menu in a Java Swing toolbar is straightforward using the JComboBox component. This component allows users to select from a list of options directly within the toolbar, enhancing the user interface of your application.

JComboBox<String> comboBox = new JComboBox<>(); // Initialize the JComboBox
comboBox.addItem("Option 1"); // Populate with options
comboBox.addItem("Option 2");
comboBox.addItem("Option 3");
comboBox.addActionListener(e -> {
    System.out.println("Selected: " + comboBox.getSelectedItem());
});  
JToolBar toolBar = new JToolBar(); // Create a toolbar
toolBar.add(comboBox); // Add JComboBox to the toolbar
JFrame frame = new JFrame(); // Create the frame
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.add(toolBar, BorderLayout.NORTH);
frame.setSize(400, 300);
frame.setVisible(true); // Display the frame

Causes

• Using JTextField instead of JComboBox for drop-down functionality.
• Not adding appropriate action listeners to menu items.

Solutions

• Replace JTextField with JComboBox for valid drop-down behavior.
• Attach ActionListeners to handle selections appropriately.

Mistake: Using an empty JComboBox without items.

Solution: Always add options to the JComboBox using `addItem()` method before adding to the toolbar.

Mistake: Failing to set the frame to be visible.

Solution: Ensure you call `frame.setVisible(true)` after adding components to the frame.