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CUSTOMER_CODE SMUDE DIVISION_CODE SMUDE EVENT_CODE APR2016 ASSESSMENT_CODE MCA4030_APR2016 QUESTION_TYPE DESCRIPTIVE_QUESTION QUESTION_ID 12947 QUESTION_TEXT Explain the life cycle of an Applet in Java. Also give the Java Applet skeleton. SCHEME OF EVALUATION The Applet life cycle uses the 4 methods: init(), start(), stop() and destroy(). •init() - The init( ) method is the first method to be called. This is where we should initialize variables. This method is called only once during the run time of the applet. •start() - The start( ) method is called after init( ). It is also called to restart an applet after it has been stopped. Whereas init( ) is called once the first time an applet isloaded, start( ) is called each time an applet’s HTML document is displayed onscreen. So, if a user leaves a web page and comes back, the applet resumes execution at start(). •stop() - The stop( ) method is called when a web browser leaves the HTML document containing the applet - when it goes to another page, for example. When stop( ) is called, the applet is probably running. You should use stop( ) to suspend threads that don’t need to run when the applet is not visible. You can restart them when start( ) is called if the user returns to the page. •destroy() - The destroy( ) method is called when the environment determines that your applet needs to be removed completely from memory. At this point, you should free up any resources the applet may be using. (2 x 4 = 8 Marks) Applet Skeleton: import java.awt.*; importjava.applet.*; /* <applet code="AppletSkel" width=300 height=100></applet> */ public class AppletSkel extends Applet { // Called first. public void init() { // initialization } /* Called second, after init(). Also called whenever the applet is restarted. */ public void start() { // start or resume execution } // Called when the applet is stopped. public void stop() { // suspends execution } /* Called when applet is terminated. This is the last method executed. */ public void destroy() { // perform shutdown activities } // Called when an applet's window must be restored. public void paint(Graphics g) { // redisplay contents of window } } ( 2 Marks) QUESTION_TYPE DESCRIPTIVE_QUESTION QUESTION_ID 72592 QUESTION_TEXT Describe the three types of operators in java Arithmetic operators description= 2.5 marks Increment and decrement description = 2.5 marks SCHEME OF EVALUATION Logical operators description = 2.5 marks Comparison operators description = 2,5 marks (2.5 * 4=Total 10 marks) QUESTION_TYPE DESCRIPTIVE_QUESTION QUESTION_ID 120576 QUESTION_TEXT What are the different Exception handling techniques? Explain with an example. Try Block Try { SCHEME OF EVALUATION //statements that may cause an exception } Nested try statement ( example) ( 3.5 marks) Catch Block try { //statements that may cause an exception } Catch ( ) { // error handling code example (3.5 marks) } finally block finally { closeFile( ); (3marks) } QUESTION_TYPE DESCRIPTIVE_QUESTION QUESTION_ID 120577 Explain in detail the access specifiers supported by Java. QUESTION_TEXT Explanation SCHEME OF EVALUATION i. Public with example (3 marks) ii. Private with example (3 marks) iii. Protected with example (4 marks) QUESTION_TYPE DESCRIPTIVE_QUESTION QUESTION_ID 120579 Briefly explain the various constants and methods used in QUESTION_TEXT i. ii. i. ActionEvent class AdjustmentEvent class ActionEvent Class: An ActionEvent is generated when a button is pressed, a list item is double-clicked, or a menu item is selected. The ActionEvent class defines four integer constants that can be used to identify any modifiers associated with an action event: ALT_MASK, CTRL_MASK, META_MASK, and SHIFT_MASK. In addition, there is an integer constant, ACTION_PERFORMED, which can be used to identify action events. (2 Marks ) ActionEvent has these three constructors: ActionEvent(Object src, int type, String cmd) SCHEME OF EVALUATION ActionEvent(Object src, int type, String cmd, int modifiers) ActionEvent(Object src, int type, String cmd, long when, int modifiers) Here, src is a reference to the object that generated this event. The type of the event is specified by type, and its command string is cmd. The argument modifiers indicates which modifier keys (ALT, CTRL, META, and/or SHIFT) were pressed when the event was generated. The when parameter specifies when the event occurred. You can obtain the command name for the invoking ActionEvent object by using the getActionCommand( ) method, shown here: String getActionCommand( ) For example, when a button is pressed, an action event is generated that has a command name equal to the label on that button. (3 marks) ii. AdjustmentEvent class An AdjustmentEvent is generated by a scroll bar. The AdjustmentEvent class defines integer constants that can be used to identify them. (2 Marks) In addition, there is an integer constant, ADJUSTMENT_VALUE_CHANGED that indicates that a change has occurred. The constructor: AdjustmentEvent(Adjustable src, int id, int type, int data) src is a reference to the object that generated this event. The id equals ADJUSTMENT_VALUE_CHANGED The type of the event is specified by type, and its associated data is data. The getAdjustable( ) method returns the object that generated the event. The type of the adjustment event may be obtained by the getAdjustmentType( ) method. (3 Marks) QUESTION_TYPE DESCRIPTIVE_QUESTION QUESTION_ID 120582 QUESTION_TEXT What is Java IDL? Explain. SCHEME OF EVALUATION 1. Java IDL is a technology for distributed objects – i.e. objects interacting on different platform across a network. IDL stands for Interface Definition Language. 2. Java IDL is similar to RMI, which supports distributed objects written entirely in the Java programming language. However, Java IDL enable objects interact regardless of whether they’re written in the Java programming language or another language such as C, C++, COBOL or others. 3. Java IDL is based on the Common Object Request Brokerage Architecture, an industry standard distributed object model. 4. A key feature of CORBA is IDL, a language –neutral Interface Definition Language. Each language that supports CORBA has its own IDL mapping and as its name implies, Java IDL supports the mapping for Java. CORBA and the IDL mappings are the work of an industry consortium known as the OMG or Object Management Group. 5. TO support interaction between objects in separate programs Java IDL provides an Object Request Broker, or ORB. The Orb is a class library that enables low level communication between Java IDL applications and other CORBA compliant applications. (10 marks)