Java Swing in Computer Science

Swing

• Java Foundation Classes (JFC) is a graphical framework for building portable Java-based graphical user interfaces.
• JFC consists of Abstract Window Toolkit (AWT), Swing, and Java 2D.
• Swing is a part of JFC that is used to create window-based applications.
• Swing components facilitate efficient graphical user interface (GUI) development.

Features of Swing

• Platform Independent: Swing components are not platform specific, and can be used on any platform.
• Lightweight: Swing components are lightweight, which helps in creating a lighter UI.
• Plugging: Swing has a powerful component that can be extended to provide support for the user interface.
• Manageable: It is easy to manage and configure Swing components, with the ability to make changes at runtime.
• MVC: Swing follows the concept of Model View Controller (MVC), which allows for changes in one component without impacting others.

Java Foundation Class

• Java Foundation Classes (JFC): JFC provides a consistent user interface for Java programs, regardless of the underlying user interface system.

Swing vs AWT

• Swing: Swing components are platform-independent, lightweight, and support pluggable look and feel.
• AWT: AWT components are platform-dependent, heavyweight, and do not support pluggable look and feel.

Component Hierarchy

• JComponent Class: JComponent class is the root of the visual component class hierarchy in JFC.
• JComponent: The JComponent class is a repository of functionality for all visual components.

Panes

• RootPane: A root pane is created when a JFrame is created.
• GlassPane: A glass pane is a transparent pane that covers the entire visible area of the root pane.
• ContentPane: A content pane is where all the visible content is placed.
• LayeredPane: A layered pane is a Swing container that holds components using the concept of layers.

Swing Components

• JLabel: JLabel is used to display a short string or an image icon.
• JTextField: JTextField is a component that allows editing of a single line of text.
• JPasswordField: JPasswordField is a component that allows editing of a single line of text, but the view indicates that something was typed, without showing the actual characters.

Example Code

• Example code is provided for JLabel, JTextField, JPasswordField, and JRootPane.### JTextArea
• Used to display and edit text
• Inherits JComponent class
• Can be customized to user's needs
• Constructors:
  • JTextArea(): constructs a new blank text area
  • JTextArea(String s): constructs a new text area with a given initial text
  • JTextArea(int row, int column): constructs a new text area with a given number of rows and columns
  • JTextArea(String s, int row, int column): constructs a new text area with a given number of rows and columns and a given initial text
• Commonly used methods:
  • append(String s): appends the given string to the text of the text area
  • getLineCount(): gets the number of lines in the text of the text area
  • setFont(Font f): sets the font of the text area to the given font
  • setColumns(int c): sets the number of columns of the text area to the given integer
  • setRows(int r): sets the number of rows of the text area to the given integer

JCheckBox

• Used to create a checkbox
• Inherits JToggleButton class
• Can be selected or deselected
• Displays its state to the user
• Constructors:
  • JCheckBox(): creates a new checkbox with no text or icon
  • JCheckBox(Icon i): creates a new checkbox with the specified icon
  • JCheckBox(Icon icon, boolean s): creates a new checkbox with the specified icon and the boolean value specifies whether it is selected or not
  • JCheckBox(String t): creates a new checkbox with the specified string
  • JCheckBox(String text, boolean selected): creates a new checkbox with the specified string and the boolean value specifies whether it is selected or not
  • JCheckBox(String text, Icon icon): creates a new checkbox with the specified string and icon
  • JCheckBox(String text, Icon icon, boolean selected): creates a new checkbox with the specified string and icon and the boolean value specifies whether it is selected or not
• Methods to add Item Listener to checkbox: +.addActionListener(ItemListener l): adds item listener to the component
  • itemStateChanged(ItemEvent e): abstract function invoked when the state of the item to which listener is applied changes
  • getItem(): returns the component-specific object associated with the item whose state changed
  • getStateChange(): returns the new state of the item
  • getSource(): returns the component that fired the item event
• Commonly used methods:
  • setIcon(Icon i): sets the icon of the checkbox to the given icon
  • setText(String s): sets the text of the checkbox to the given text
  • setSelected(boolean b): sets the checkbox to selected if the boolean value passed is true or vice versa
  • getIcon(): returns the image of the checkbox
  • getText(): returns the text of the checkbox

JRadioButton

• Used to create a radio button
• Used to select one option from multiple options
• Added to a ButtonGroup to select only one radio button at a time
• Methods used:
  • JRadioButton(): creates a new unselected radio button with no text
  • setButtonGroup(ButtonGroup G): adds the radio button to a ButtonGroup
  • isSelected(): returns a boolean value indicating whether the radio button is selected or not

JComboBox

• Used to create a combo box
• Inherit JComponent class
• Can be editable or read-only
• Constructors:
  • JComboBox(): creates a new empty combo box
  • JComboBox(ComboBoxModel M): creates a new combo box with items from the specified ComboBoxModel
  • JComboBox(E[] i): creates a new combo box with items from the specified array
  • JComboBox(Vector items): creates a new combo box with items from the specified vector
• Commonly used methods:
  • addItem(E item): adds the item to the combo box
  • addItemListener(ItemListener l): adds an item listener to the combo box
  • getItemAt(int i): returns the item at the specified index
  • getItemCount(): returns the number of items in the combo box
  • getSelectedItem(): returns the selected item
  • removeItemAt(int i): removes the item at the specified index
  • setEditable(boolean b): sets the combo box to be editable or not

JList

• Used to display a set of objects and allows the user to select one or more items
• Inherit JComponent class
• Constructors:
  • JList(): creates a new empty list
  • JList(E[] l): creates a new list with the elements of the specified array
  • JList(ListModel d): creates a new list with the specified ListModel
  • JList(Vector l): creates a new list with the elements of the specified vector
• Commonly used methods:
  • getSelectedIndex(): returns the index of the selected item
  • getSelectedValue(): returns the selected value
  • setSelectedIndex(int i): sets the selected index
  • setSelectionBackground(Color c): sets the background color of the list
  • setSelectionForeground(Color c): sets the foreground color of the list

JDBC

• Java Database Connectivity
• Used for database-independent connectivity between Java and a wide range of databases
• API provides a set of interfaces that allows for portable access to an underlying database
• JDBC components:
  • DriverManager: manages a list of database drivers
  • Driver: handles the communication with the database server
  • Connection: represents the communication context
  • Statement: used to submit SQL statements to the database
  • ResultSet: holds the data retrieved from the database
  • SQLException: handles errors that occur in a database application
• JDBC Architecture:
  • Two-tier architecture: Java application talks directly to the data source
  • Three-tier architecture: Java application talks to a middle tier, which talks to the data source
• JDBC drivers:
  • Type-1 driver: JDBC-ODBC bridge driver
  • Type-2 driver: Native-API driver
  • Type-3 driver: Network Protocol driver
  • Type-4 driver: Thin driver
• JDBC statements:
  • Statement: general-purpose access to the database
  • PreparedStatement: used when you plan to use the SQL statements many times
  • CallableStatement: used to access the database stored procedures### Creating Statement Objects
• A Statement object needs to be created using the Connection object's createStatement() method before it can be used to execute a SQL statement.
• The createStatement() method returns a Statement object, which can then be used to execute a SQL statement with one of its three execute methods.

Execute Methods

• boolean execute(String SQL): Returns a boolean value of true if a ResultSet object can be retrieved; otherwise, it returns false.
• int executeUpdate(String SQL): Returns the number of rows affected by the execution of the SQL statement.
• ResultSet executeQuery(String SQL): Returns a ResultSet object.

Closing Statement Objects

• A Statement object should be closed to save database resources.
• A simple call to the close() method will do the job.
• If the Connection object is closed first, it will also close the Statement object.

PreparedStatement Objects

• The PreparedStatement interface extends the Statement interface, providing additional functionality.
• It allows for the flexibility of supplying arguments dynamically.
• Creating a PreparedStatement object is similar to creating a Statement object, but with the prepareStatement() method.
• Parameters in JDBC are represented by the ? symbol, known as the parameter marker.
• Values for every parameter must be supplied before executing the SQL statement using the setXXX() methods.

Execute Methods with PreparedStatement

• The execute methods with PreparedStatement are similar to those with Statement, but with the added functionality of using SQL statements that can input parameters.

Closing PreparedStatement Objects

• A PreparedStatement object should be closed to save database resources.
• A simple call to the close() method will do the job.
• If the Connection object is closed first, it will also close the PreparedStatement object.

CallableStatement Objects

• The CallableStatement object is used to execute a call to a database stored procedure.
• Creating a CallableStatement object is similar to creating a PreparedStatement object, but with the prepareCall() method.
• Three types of parameters exist: IN, OUT, and INOUT.
• The registerOutParameter() method binds the JDBC data type to the data type that the stored procedure is expected to return.

Closing CallableStatement Objects

• A CallableStatement object should be closed to save database resources.
• A simple call to the close() method will do the job.
• If the Connection object is closed first, it will also close the CallableStatement object.

ResultSet

• The ResultSet interface represents the result set of a database query.
• A ResultSet object maintains a cursor that points to the current row in the result set.
• The methods of the ResultSet interface can be broken down into three categories: navigational methods, get methods, and update methods.

Connection Modes

• Connection with URL: DriverManager.getConnection(url)
• Connection with URL, user, password: DriverManager.getConnection(url, user, password)
• Connection with URL and Properties: DriverManager.getConnection(url, properties)
• Connection via Try-With-Resources: try (Connection connection = DriverManager.getConnection(url, user, password)) { ... }

JDBC Transactions

• If the JDBC Connection is in auto-commit mode, every SQL statement is committed to the database upon its completion.
• To enable manual-transaction support, use the setAutoCommit() method.
• Commit and rollback changes using the commit() and rollback() methods.

Commit and Rollback

• conn.commit(): Commits the changes to the database.
• conn.rollback(): Rolls back the changes to the database.

Using Savepoints

• The Savepoint interface gives additional transactional control.
• Setting a savepoint defines a logical rollback point within a transaction.
• conn.setSavepoint("Savepoint1"): Defines a new savepoint.
• conn.rollback(savepoint1): Rolls back work to the specified savepoint.

Batch Updations

• Batch Processing allows grouping related SQL statements into a batch and submitting them with one call to the database.
• The addBatch() method is used to add individual statements to the batch.
• The executeBatch() method is used to start the execution of all the statements grouped together.
• The clearBatch() method removes all the statements added to the batch.

Batching with Statement Object

• Set auto-commit to false using setAutoCommit().
• Add SQL statements to the batch using addBatch().
• Execute all the SQL statements using executeBatch().
• Commit all the changes using commit().