ADVANCED GUIS AND GRAPHICS - Java Programming: From Problem Analysis to Program Design - page 860

//Create a text area and place it in the EAST region
//and set the font of this text area.
bill = new JTextArea();
pane.add(bill, BorderLayout.EAST);
bill.setFont( new Font("Courier", Font.PLAIN, 12));

//Create a button and place it in the SOUTH region and
//add an action listener.
JButton button = new JButton("Selection Completed");
pane.add(button, BorderLayout.SOUTH);
button.addActionListener( this );
We need another array to keep track of the prices of the various items.

static double [] yourChoicesPrices = {1.45, 0.80, 0.75, 2.75,
2.50, 2.00, 1.50, 3.00,
0.90, 1.00, 1.75};
The following statements set the size of the window and set its visibility to true :

setSize(500, 360);
setVisible( true );
Recall that when an action event is generated by a button, the method
actionPerformed is invoked. When the user clicks the button, the program must
compute the subtotal, tax, and total, and display the result in the text area. The
instructions to perform these tasks are placed in the method actionPerformed ,
which is described next.

As noted previously, the method actionPerformed is executed when the user clicks
the button.The method actionPerformed calculates and displays the bill. We write
the method displayBill that computes the bill and displays it using the text area.
The method actionPerformed invokes the method displayBill to display the
bill. The definition of the method actionPerformed is:

Method
actionPerformed

public void actionPerformed(ActionEvent event)
{

if (event.getActionCommand().equals("Selection Completed"))
displayBill();

}

The method displayBill first needs to identify the items selected by the user. The
method getSelectedIndices of the JList will return an array of indices. Because
we need an integer array to hold these indices, we might need the following Java
statements:

Method
displayBill