M257 Putting Java to work

Transcription

1 Arab Open University Faculty of Computer Studies Course Examination Spring 2010 M257 Putting Java to work Exam date: May 2010 Time allowed: 2.5 hours Form: X A B Student name/ Section number: Tutor Name: Branch Name: IMPORTANT INSTRUCTIONS 1) This exam has 3 parts and ALL questions must be answered by students. 2) Please go through all the questions before you start answering them. This will help prevent too much time being spent at the start. 3) This exam consists of (7 to 8 pages including 1 title page in the beginning, and 1 examhandbook page at the end). 4) On last page, you will find some notes about the Java language that may be useful to you when answering some of the questions of the exam. 5) Student handbooks are NOT permitted in this examination. 6) The use of electronic devices that could have a memory is NOT permitted. 7) At the end of the examination: Check that you have written your student ID, name and your section number on the first page. Put your answer book and your question paper together and give them to the exam invigilator. 1 of 7

2 Part I: MCQs and FIBs Multiple Choice Questions (24 marks) (8 x 1.5 marks) SAMPLE QUESTIONS 1. When we say that Java programs are strictly checked by software before they run, this means Java is... a. secure c. interpreted b. robust d. threaded 2... translates and executes Java bytecode. a. Java interpreter c. Java debugger b. Java compiler d. Java disassemble 3... helps to look for errors in programs. a. Java interpreter c. Java debugger b. Java compiler d. Java disassemble 4... methods have an effect on the state of the object; for example, anobject.setx(); a. Accessor c. Constructor b. Mutator d. All of the above is an example of checked exceptions. a. RunTimeException c. Error b. FileNotFoundException d. None of the above etc. 2 of 7

3 Part II: Essay (26 marks) SAMPLE QUESTIONS 1. What do we mean when we say that Java is a secure language? This means that Java ensures that programs running over networks cannot damage your computer files or introduce viruses. 2. a) What is meant by name clash in Java? b) How can we solve a name clash problem? Give an example for both (a) and (b). a) Name clash: it means two classes with the same name in different packages that are imported to a java program.for example: import java.util.*; import java.sql.*;... Date d1 = new Date(DATE_IN); //Date is ambiguous both libraries have a class with the name Date and thus we get an ambiguous name. b) Solution (1): to use the fully qualified name of the Date class (i.e. Method1 above) java.sql.date d1 = new java.sql.date(date_in); Solution (2): to import only those classes you actually use, for example: import java.util.arraylist; import java.sql.* 3. Assume we have two classes named Employee and Department. a) Write one line of Java code that declares an ArrayList, list1, that will hold 10 Employee references. b) Write one line of Java code that declares a HashMap, list2, that will link 10 Employee references to 10 Department references. a) ArrayList<Employee> list1 = new ArrayList<Employee>(10); b) HashMap<Employee,Department> table2 = new HashMap<Employee,Department>(10); 3 of 7

4 Part III: Problem solving (50 marks) This part includes questions that focus on writing/analyzing Java code. For any question that requires writing Java code, you must: Use indentation to help make the structure of your program clear. Import necessary Java libraries, whenever appropriate. The questions are of the type: - Rewrite the following code segment using a different technique. - Develop a class with a specific design. - Consider some java code and answer questions about it. These questions may include for example: - Display the output if the input is so and so. - What happens if the following lines of code are removed or added? - Add more code that does so and so. - Etc. Sample questions are as follows: SAMPLE QUESTIONS 1. Write a simple program to read two integers from the user and display the sum of them. Use the Scanner class to read the input. Import any necessary java libraries. 2. Write Java code to display the whole content of a text file, C:\test.txt, to the user. Use the BufferedReader class to read the file. 3. Consider the following Java code: 4 of 7

5 a) Describe or draw the output of the above code. b) Draw the output of the above code if line 8 is deleted. Explain your answer. c) Create an ActionListener object and register it with the gobutton object so that the system prints (using System.out.println) the user name and address once the gobutton is clicked. In your answer, just write the required lines of code and clearly state where the added code should be inserted. a) b) The default layout manager will be used --> BorderLayout. And since the code doesn t describe where each GUI element will be put, then all GUI elements will be put on top of each other at the central area of the frame. The last element quitbutton will be the only one visible since it is the ast one added. 5 of 7

6 c) we should add the following anywhere after defining the gobutton: gobutton.addactionlistener(new GoHandler()); --> add the following after the main method: private class GoHandler implements ActionListener{ public void actionperformed(actionevent e) { System.out.println("Name: " + username.gettext()); System.out.println(" " + user address.gettext()); } [END OF QUESTION PAPER] GOOD LUCK! 6 of 7

7 EXAM HANDBOOK This part include useful hints about some Java aspects that you may find useful while you answer the questions of the exam. For example, see the first line: Exceptions IllegalArgumentException This is raised when some object or primitive is given a value which is not expected, i.e. a value outside the specified range. Java library packages (J2SE) Java library packages (J2ME) Event handling etc 7 of 7