Swing Interfaces with Sorting and Searching

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Chapter 7

• Swing Interfaces with Sorting
  and Searching

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Chapter Objectives

• List features of the Java Foundation Classes
  (JFC)
• Differentiate between AWT and Swing components
• Create a JFrame application
• Sort data in parallel arrays

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Chapter Objectives

• Use the keyword, super, in a constructor method
• Create a tool tip
• Use methods associated with JPanels, JComboBoxes,
  JLabels, JTextPanes, and JScrollPanes
• Use Tabs and Styles in a JTextPane

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Chapter Objectives

• Use methods associated with the Document class
• Perform linear searches
• Incorporate Look and Feel methods in an interface

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Introduction

• Swing components are GUI components
• Provides a wide range of objects and methods to
  build user interfaces
• Includes lightweight Java-based components that
  allow programmers to tailor windows
• The application in this chapter stores a DVD
  collection of classic movies
• GUI and menu system use Swing components
• A formatted list is displayed with scrolling
  capabilities
• The program allows insertions, as well as sorts
  and searches of the list by title, studio, or year

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Classics on DVD Application
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Problem Analysis

• Insert
• Users can enter a new movie title, studio, and
  year
• Search
• User enter a search argument for a specific field
  and the program finds and displays the results
• Sort
• Users request a alphanumeric sort of all data
  based upon a certain field
• The program reorders all accompanying data based
  on that field

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Design the Solution

• Scrollable text area to display a formatted movie
  list
• Drop-down list for sort choices
• Menu options with shortcut keys underlined
• A shortcut key is a special key combination used
  to invoke commands on a menu
• Provide users with different samples of formatted
  text
• Font family, italic, bold, and large attributes

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Menu Storyboard
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Program Design

• Data storage
• Since this program is a prototype, data can be
  stored during program execution instead of in a
  database
• Three parallel arrays, one each for the title,
  studio, and year
• Subscript is the same for each piece of movie
  data, forming a record across the arrays
• Searching
• Linear search looks through the list sequentially
• Sorting
• Users specifies a field, the corresponding array
  is sorted, and the other arrays are modified
  accordingly

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Sorting parallel arrays
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Swing and Java Foundation Classes
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Swing versus AWT

• Swing components are not implemented with native
  code and have more functionality than AWT
  components

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Swing Container Hierarchy

• Containers play a more important role in Swing
  than in AWT
• Swing components should be placed in a top-level
  Swing container
• First, use a content pane to hold the components,
  and then add the content pane to the top-level
  container
• The getContentPane() method creates a Container
  instance
• Avoid combining complex AWT components in the
  same container as Swing components
• When Swing and AWT components overlap, the
  heavyweight component is painted on top

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Extending JFrame

• JFrame is a top-level container
• Programs implementing ActionListener must include
  an actionPerformed() method before they will
  compile successfully

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Class-Level Components

• Visible to all other methods within the class
• JLabel can display labels, borders, and images
• JComboBox is a drop-down list and can be editable
• The default is uneditable
• JTextPane is a text component that displays with
  graphic attributes
• Each paragraph has a logical style with default
  attributes
• Three String arrays

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Constructing Parallel Arrays

• Populate the arrays as they are constructed
• The array length is automatically set equal to
  the number of items in the constructor method
• An alternative method would be to fill the arrays
  during execution by reading in the values from a
  database

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Using the super keyword

• When inheriting from another class, a constructor
  must call a constructor of its immediate
  superclass
• A superclass default constructor can be called
  implicitly
• An explicit call, if needed, is made using the
  keyword, super

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Creating a JMenuBar

• JMenuBar creates an object that can be set at the
  top of a JFrame through the setJMenuBar() method
• JMenu objects are the commands on a JMenu bar
• JMenuItems display on the drop-down list for each
  JMenu
• Mnemonic keys can be set for a Menu or MenuItem
  object
• A mnemonic key is the keyboard letter which, when
  combined with another key, activates the object
• The mnemonic key is specified with a VK keycode
  from the KeyEvent class

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Creating a Menu System

• setMnemonic()
• Sets the keyboard mnemonic for a Menu or MenuItem
  object
• Object.setMnemonic(KeyEvent.keycode)
• setDisplayedMnemonicIndex()
• Assigns the shortcut key to a letter in the
  commands keyword, underlining the letter
• setActionCommand()
• Assigns a String that can be evaluated in the
  actionPerformed() method
• addActionListener()
• Causes the click of the menu command to trigger
  an event
• add()
• Adds its argument to the menu system

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Creating the Content Pane

• Write a method to return the Container object
  which acts as a content pane
• Container is the superclass of all containers in
  the API
• setToolTipText()
• The tool tip displays when the mouse moves over
  the object
• JScrollPane
• Facilitates a scrollable view of JTextPane
• The viewport is the visible part of the pane at
  any given time
• Uses a Dimension object to set the preferred size
  
• setVerticalScrollBarPolicy() uses a constant to
  set the scrollbar
• getContentPane() creates an instance of the
  Container
• Can be used with JApplets or JFrames

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createContentPane()
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Tabs and Styles

• TabStop class
• Creates predetermined tab positions
• TabSet class
• Comprised of TabStops and is used to locate a
  specific TabStop
• StyleContext class
• Contains a pool of styles which are reused by
  various style definitions
• AttributeSet class
• Uses a defined StyleContext to set attributes for
  an object
• Style class
• Stores a collection of attributes associated with
  an element in a document

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setTabsAndStyles()
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The Document Class

• Creates a container for Swing text components
• Useful for appending and refreshing text-based
  Swing components

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addTextToTextPane() Method
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The actionPerformed() Event

• Use getActionCommand() to retrieve the String
  assigned to a component that can have multiple
  states
• Use getSource() to retrieve the clicked object
• If the combo box was clicked, the index number is
  compared in a switch statement to specify the
  sort
• If Insert was clicked, enlargeArray() creates a
  new array to accommodate the new movie data
• New data is sent to each array, which is then
  sorted
• If Search was clicked, the field name and array
  are sent to the search() method

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Coding the enlargeArray() Method

• Accepts an array and returns a new array that is
  one element longer
• The actionPerformed() method inserts the new data
  at the end of the new array

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Sorting an Array

• Bubblesort
• When a pair of elements is examined, the
  interchanged element moves to the top of the
  array
• Selection sort
• The array is searched for its lowest-value
  element, which is then positioned at the
  beginning of the array
• The process is repeated for each element, placing
  the elements in the next unsorted location
• Insertion sort
• Creates a new array and inserts the values in
  order
• Merge sort
• Takes two previously sorted arrays of the same
  data type and sorts them into one list

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sort()
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Searching an Array

• Linear search
• Looks sequentially through the array one element
  at a time
• Necessary when data is not in order
• Inefficient for large amounts of data
• Binary search
• Suited for large arrays of sorted data
• The search data is first compared with the middle
  element
• If search data is lower, the middle element
  become the new high
• If search data is higher, the middle element
  becomes the new low
• Searches continue to reduce the array by one-half
  until a match is found

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Linear search
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Binary search
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search()
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Look and Feel

• Gives any program using Swing programs a choice
  of how windows, title bars, and components will
  appear
• Java look and feel, Windows look and feel, etc.
• The choices are called window decorations
• Developers can design their own Look and Feel
  objects

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The main() method

• setDefaultLookandFeelDecorated() method
• Construct an instance of the DVD object
• setDefaultCloseOperation() controls the action of
  the close button
• Wrap the create Menu and Pane methods inside the
  set Menu and Pane methods

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Testing

• Compile the program and fix any errors
• Test the sorting of the different fields
• Test the addition of a DVD title, studio, and
  year
• Test the search capabilities with a specific
  title, studio, and year
• Test the other menu commands and shortcut keys

46
Chapter Summary

• List features of the Java Foundation Classes
  (JFC)
• Differentiate between AWT and Swing components
• Create a JFrame application
• Sort data in parallel arrays

47
Chapter Summary

• Use the keyword, super, in a constructor method
• Create a tool tip
• Use methods associated with JPanels, JComboBoxes,
  JLabels, JTextPanes, and JScrollPanes
• Use Tabs and Styles in a JTextPane

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Chapter Summary

• Use methods associated with the Document class
• Perform linear searches
• Incorporate Look and Feel methods in an interface

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Chapter 7 Complete

• Swing Interfaces with Sorting
  and Searching