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CS 240 Exam 1
Computer Science II
Spring 2002 2/6/02
Page 1
Name _____________________________
Explain or give the UNIX or vi commands or keystrokes to do the following tasks.
[27 pts]
1. Display only filenames that have the .java extension. _______________________[2]
2. Display all filenames (including the special ones starting with a period) found in /academic/cs2
________________________ [2]
3. Delete all files with extension .class in the current directory. ____________________________[2]
4. Create a subdirectory called classes. ___________________________[2]
5. Move all .class files in your current directory to the new subdirectory classes
____________________________________ [2]
6. Set your current working directory to the new classes subdirectory ________________________[2]
7. Display the contents of the file program.java one screen at a time ______________________[2]
8. Begin capturing the screen display to a file for printing later ____________________ [1]
9. Print the file typescript to the local printer using the enscript formatter ____________________________[2]
10. Start the visual editor on file program.java ______________________[2]
11. What keystroke terminates a program in Unix?____
What keystroke designates end of input in Unix?____[2]
12. Define a symbol dir as a synonym (same meaning) as ls _________________________ [3]
13. Run the program filter using the file data for input and pipe the output stream through more.
__________________________________________________[3]
14. Give the keystroke(s) in vi to perform the following actions
[8 pts]
_____undo the previous action (1 character)
_____exit and save the file (2 chars)
_____ start insertion mode (1 char)
_____ move the cursor down 10 lines (3 chars)
_____ delete the current line (2 chars)
_____ end insert mode (1 char)
_____ repeat the previous editing operation (1 char)
_____ exit and do not save the file (3 chars)
CS 240 Exam 1
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15. Collections.
[10 pts]
a. Connect the four elements below into a purely linear collection with arrows starting at element A and
ending at element D [3].
A
D
B
C
b. Connect the four elements below into a hierarchical structure with the root (start) as B with C as an
intermediate node. [3]
A
D
B
C
c. Name three general operations that we can perform on collections.
___________________
___________________
___________________
16. Abstract Control Structures. (True/False)
[5 pts]
a. ____ The if-then-else statement is a form of a selection control structure.
b. ____ The switch statement is a form of an iterative control structure.
c. ____ A void function is one that should not have a return value.
d. ____ The for loop can always be transformed into a while loop.
e. ____ The break statement is used only in the switch statement.
17. Programming principles. Fill in the blank.
[10 pts]
a. The Information Hiding Principle specifies that the user of a module is provided only the necessary
information to _________ the module and that the ___________________________ is provided only
the necessary information to ______________________ the module.
b. A ________-condition specifies what must be true at the beginning of a function and a
____________________ specifies what must be true at the end of a function. These assertions
provide a form of a contract between the ____________ and the implementer.
c. Testing a module knowing its function but not necessarily its implementation is called ___________- box
testing while ___________ -box testing ensures each control path is tested in the implementation.
d. The part of speech (noun, verb, adjective) that should be used for an instance variable is a/an __________
and the part of speech that should be used for a void function is a/an _____________.
CS 240 Exam 1
Page 3
18. Java concepts (True/False)
[10 pts]
a. _____ Each Java class should defined in its own separate file and that file name must match the class name.
b _____ To execute the bytecodes of a Java program you must use a Java Virtual Machine.
c. _____ Garbage collection must be explicitly invoked by the user to recover unreferenced objects.
d. _____ The toString function that can be defined for each class is an example of polymorphism.
e. _____ Strings in Java are immutable.
f. _____ A class that is inherited from an existing class is the superclass.
g. _____A protected instance variable is an inheritable public variable.
h. _____Every class ultimately is a subclass of Object.
i. _____ Two strings can be compared with ==
j. _____ The import statement is a reference to one or more supporting class files.
19. Number the steps of the software development cycle (Waterfall method) from 1 to 6 in correct order.
[5 pts]
_____ Design
_____ User request
_____ Analysis
_____ Integration
_____ Integration
_____ Maintenance
20. What is meant and gained by separating the view of a GUI solution from the model of its solution?
[5 pts]
CS 240 Exam 1
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21. Below is a segment of code similar from class and your project. Assume classes Circle and Rectangle are
subclasses of Shape.
[20 pts]
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Circle [] circles;
circles = new Circle[10];
circles[0] = new Circle (1,1,2);//(x,y,radius)
circles[1] = new Circle (2,2,3);
Shape shapes[] = new Shape[10];
shapes[0] = new Circle(1,2,3);
shapes[1] = circles[1];
shapes[2] = new Rectangle(2,3,4,4);//(x,y,length,width)
shapes[3] = circles[0];
shapes[4] = new Rectangle(3,4,5,1);
double totalArea = 0;
for(i=0; i<5; i++){
System.out.println(shape[i]);
if shapes[i] instanceof Rectangle){
totalArea += shape[i].area();
}
}
System.out.println(totalArea);
a. Describe what lines 1 and 2 accomplish.
b. What is being called in lines 3 and 4?
c. Draw a picture of the memory layout as a result of lines 6-11.
d. Describe what function(s) is/are called in line 15.
e. What is the value of the last println in line 20?