Building Applications with Buttons

• Example: investment viewer program; whenever button is clicked, interest is added, and new balance is displayed
  
• Construct an object of the JButton class:
  JButton button = new JButton("Add Interest");
• We need a user interface component that displays a message:
  JLabel label = new JLabel("balance=" + account.getBalance());
• Use a JPanel container to group multiple user interface components together:
  JPanel panel = new JPanel();
  panel.add(button);
  panel.add(label);
  frame.add(panel);