Chapter 13, Problem 3AW

Explanation of Solution

Lists:

• A list is a component which is used to display a list of items.
• It is also used to allow the user to select an item from the list.
• In Java programming, the list is created by using “JList” component.
• Once the user create an object of the “JList” class, user needs to pass the array of objects to the constructor.
  • The format for this constructor: “JList (Object[] array)”
• The “JList” component always uses the array to make the list of items.

Adding a Scroll Bar to a List:

• Suppose, if a list contains too many elements to be shown at once, user can use a scroll bar to display a list with many number of items.
• A scroll bar is used to allow the user simply uses the scroll through the list of items.
• In Java GUI applications, list components do not automatically display a scroll bar.
• Using the below steps, user is able to display a scroll bar on a list component.
  • Assign the number of visible rows for the list component using “setVisibleRowCount” method.
  • Then add the list component to an object of scroll pane.
    • User can create the object of scroll pane using “JScrollPane” class.
  • Finally add the object of scroll pane to any other container such as panels.

Example:

The example for list component is shown below:

//Store the fruit names in "String" array

String[] fruitNames = {"Apple", "Orange", "Grapes", "Banana"};

//Pass the array of "fruitNames" to "JList" class

JList fruitsList = new JList(fruitsNames);

//Set visible number of rows for fruit lists

fruitsList.setVisibleRowCount(3);

//Create a scroll pane

JScrollPane sampleScroll = new JScrollPane(fruitsList);

//Create a panel

JPanel samplePanel = new JPanel();

//Add the scroll pane to panel

samplePanel.add(sampleScroll);

//Add the panel to the "JFrame" object's contentPane

add(samplePanel);

From the above code,

• The fruit names are stored in the “String” array. The object of given “String” array is “fruitNames”.
• The pass the array of “fruitNames” to “JList” constructor...