Lab5. Wooseok Kim

Transcription

1 Lab5 Wooseok Kim

2 Question Answer Points 1 A or B 8 2 A 8 3 D for class 10 for main 5 points for output 5 D or E 8 6 B D 8 9 C 8 10 B 8

3 Question Answer Points 11 D 8 12 B 8 13 A 8 14 A or B or D 8 15 E 8 16 B 8 17 A 8 18 C 8 19 nextint( 21 ) for for for correct substring 10 for correct call to length() 5 for correct output

4 Question 1 Comments should be A) rephrase the code it explains in English B) be insightful and explain what the instruction s intention is C) only be included in code that is difficult to understand D) Be used to define variables whose names are not easy to understand E) all of the above

5 Question 2 A unique aspect of Java that allows code compiled on one machine to be executed on a machine of a different hardware platform is Java s A) bytecodes B) syntax C) use of objects D) use of exception handling E) all of the above

6 Question 2

7 Question 3 An error in a program that results in the program outputting $100 instead of the correct answer, $250 is A) A programmer error B) A syntax error C) A run-time error D) A logical error E) A snafu

8 Question 3 B) A syntax error Compile Error C) A run-time error 12 / 0 =? D) A logical error Incorrect Answer

9 Question 4 Write a Java program that will display on two separate lines your name and your major.

10 Question 4 (Grading Guideline) 5 points for having the keyword class and a reasonable class name in the right place 2 points each for static, void, main(), String[], args 5 points for output the name and the major

11 Question 5 Consider the following statement: This statement will output lines of text A) 1 B) 2 C) 3 D) 4 E) 5

12 Question 5 1st line 2nd line 3rd line 4th line

13 Question 5 1st line 2nd line 3rd line 4th line Real output has 5 lines because of /r /r: Carrage Return

14 Question 6 If x is an int and y is a float, all of the following are legal except which assignment statement? A) y = x; B) x = y; C) y = (float) x; D) x = (int) y; E) all of the above are legal

15 Question 6 If x is an int and y is a float, all of the following are legal except which assignment statement? A) y = x; B) x = y; int < float C) y = (float) x; D) x = (int) y; E) all of the above are legal

16 Question 7 What will be the result of a in the following assignment statement? Assume b = 5 and c = 10.

17 Question 7 (Grading Guideline) 15 pionts Up to 10 points partical credit if they have some correct work

18 Question 8 Which library package would you import to use NumberFormat and DecimalFormat? A) java.beans B) java.io C) java.lang D) java.text E) java.util

19 Question 9 QuestionNineAndTen computes A) The correct average of x, y and z as a double B) The correct average of x, y and z as an int C) The average of x, y, and z as a double, but the result may not be accurate D) The sum of x, y and z E) The remainder of the sum of x, y and z divided by 3

20 Question 9 QuestionNineAndTen computes C) The average of x, y, and z as a double, but the result may not be accurate int = x + y + z int = int / 3 However, average is double

21 Question 10 What is output if x = 0, y = 1 and z = 1? A) 0 B) 0.0 C) D) E) 0.67 double average = ( ) / 3 = 2 / 3 = 0.0 if int average? The answer is 0

22 Question 11 In order to create a constant, you would use which of the following Java reserved words? A) private B) static C) int D) final E) class

23 Question 12 In Java, a variable of type boolean will store either a 0 or a 1 A) true B) false

24 Question 12 In Java, a variable of type boolean will store either a 0false or a 1true A) true B) false

25 Question 13 In Java, a variable may contain A) a primitive value or an object reference B) a package C) a method D) a class E) any of the above

26 Question 14 (Dropped) What happens if you attempt to use a variable before it has been initialized? A) A syntax error may be generated by the compiler B) A runtime error may occur during execution C) A garbage or uninitialized value will be used in the computation D) A value of zero is used if a variable has not been initialized E) Answers A and B are correct

27 Question 14 (Dropped) What happens if you attempt to use a variable before it has been initialized? A) A syntax error may be generated by the compiler B) A runtime error may occur during execution D) A value of zero is used if a variable has not been initialized

28 Question 15 What is the function of the dot operator? A) It serves to separate the integer portion from the fractional portion of a floating point number B) It allows one to access the data within an object when given a reference to the object C) It allows one to invoke a method within an object when given a reference to the object D) It is used to terminate commands (much as a period terminates a sentence in English) E) Both B and C are correct

29

30 Question 16 In Java, instantiation means A) noticing the first time something is used B) creating a new object of the class C) creating a new alias to an existing object D) launching a method E) none of the above

31

32 Question 17 An alias when A) Two different reference variables refer to the same physical object B) Two different numeric variables refer to the same physical object C) Two different numeric variables contain identical values D) Two variables have the same names E) none of the above

33

34 Question 18. An API is A) an Abstract Programming Interface B) an Application Programmer s Interface C) an Application Programming Interface D) an Abstract Programmer s Interface E) an Absolute Programming Interface

35 Question 19. Complete the following assignment statement that generates a random number between 20 (inclusive) to 40 (inclusive).

36 Question 20 Given a String object Computer Science whose object reference is major, use the object reference to invoke proper String instance methods to create a substring containing Sci, calculate the length of the substring, display both the substring and its length on the same line. String major = new String( Computer Science ); String substringofmajor; //Store the substring of major int lengthofmajor; //Store the length of the substring

37 Question 20

38 Question 20 (Grading Guideline) 25 points 10 for correct substring call take off 5 points if the numbers are not correct 10 for correct call to length() 5 for correct output: the substring and it s length must be on the same line