studio-plugin-snippet-toolwindow2.java

public class ToolWindowHandler implements ToolWindowFactory {
    private JPanel toolWindowContent;
    private JTextField txtName;
    private JButton btnGo;
    private JLabel lblHello;

    @Override
    public void createToolWindowContent(@NotNull Project project, @NotNull ToolWindow toolWindow) {
        ContentFactory contentFactory = ContentFactory.SERVICE.getInstance();
        Content content = contentFactory.createContent(toolWindowContent, "", false);
        toolWindow.getContentManager().addContent(content);

        btnGo.addActionListener(new ActionListener() {
            @Override
            public void actionPerformed(ActionEvent e) {
                lblHello.setText("Hello " + txtName.getText() + " o/");
            }
        });
    }
}