Object-Oriented Software Design Chapter 8 Java Software Solutions Global Edition Lewisloftus Arrays Multiplechoice Questions For The

Java Software Solutions, 8e, Global Edition (Lewis/Loftus)

Chapter 8 Arrays

8.1 Multiple-Choice Questions

For the questions below, assume values is an int array that is currently filled to capacity, with

the following values:

1) What is returned by values[3]?

A) 9

B) 12

C) 2

D) 6

E) 3

2) What is the value of values.length?

A) 0

B) 5

C) 6

D) 7

E) 18

3) Which of the following loops would adequately add 1 to each element stored in values?

A) for (j=1; j<values.length; j++) values[j]++;

B) for (j=0; j<values.length; j++) values[j]++;

C) for (j=0; j<=values.length; j++) values[j]++;

D) for (j=0; j<values.length-1; j++) values[j]++;

E) for (j=1; j<values.length-1; j++) values[j]++;

4) The statement System.out.println(values[7]); will

A) output 7

B) output 18

C) output nothing

D) cause an ArrayOutOfBoundsException to be thrown

E) cause a syntax error

5) Which of the following is a legal way to declare and instantiate an array of 10 Strings?

A) String s = new String(10);

B) String[10] s = new String;

C) String[ ] s = new String[10];

D) String s = new String[10];

E) String[ ] s = new String;

6) In Java, arrays are

A) primitive data types

B) objects

C) interfaces

D) primitive data types if the type stored in the array is a primitive data type and objects if the

type stored in the array is an object

E) Strings

7) The “off-by-one” error associated with arrays arises because

A) the first array index is 0 and programmers may start at index 1, or may use a loop that goes

one index too far

B) the last array index is at length + 1 and loops may only iterate to length, missing one

C) the last array element ends at length – 1 and loops may go one too far

D) programmers write a loop that goes from 0 to length – 1 whereas the array actually goes from

1 to length

E) none of the above, the “off-by-one” error has nothing to do with arrays

8) What does the following code do? Assume list is an array of int values, temp is some

previously initialized int value, and c is an int initialized to 0.

for (int j = 0; j < list.length; j++)

if (list[j] < temp) c++;

A) It finds the smallest value and stores it in temp

B) It finds the largest value and stores it in temp

C) It counts the number of elements equal to the smallest value in list

D) It counts the number of elements in list that are less than temp

E) It sorts the values in list to be in ascending order

9) Which of the following lists of numbers would accurately show the array after the first pass

through the Selection Sort algorithm?

A) 9, 4, 12, 2, 6, 8, 18

B) 4, 9, 12, 2, 6, 8, 18

C) 2, 4, 12, 9, 6, 8, 18

D) 2, 4, 6, 8, 9, 12, 18

E) 2, 4, 9, 12, 6, 8, 18

10) Which of the following lists of numbers would accurately show the array after the second

pass of the Selection Sort algorithm?

A) 9, 4, 12, 2, 6, 8, 18

B) 2, 4, 9, 6, 12, 8, 18

C) 2, 4, 12, 9, 6, 8, 18

D) 2, 4, 6, 8, 9, 12, 18

E) 2, 4, 12, 6, 8, 9, 18

11) Which of the following lists of numbers would accurately show the array after the fourth

pass of the Selection Sort algorithm?

A) 9, 4, 12, 2, 6, 8, 18

B) 2, 4, 6, 9, 12, 8, 18

C) 2, 4, 6, 8, 9, 12, 18

D) 2, 4, 6, 9, 8, 12, 18

E) 2, 4, 6, 8, 12, 9, 18

12) How many passes will it take in all for Selection Sort to sort this array?

A) 2

B) 4

C) 5

D) 6

E) 7

13) What does the following code do?

Scanner scan = Scanner.create(System.in);

int value1 = scan.nextInt( );

int value2 = scan.nextInt( );

bars[value1] += value2;

A) adds 1 to the number of bars sold by child value1 and child value2

B) adds 1 to the number of bars sold by child value1

C) adds value1 to the number of bars sold by child value2

D) adds value2 to the number of bars sold by child value1

E) inputs a new value for the number of bars sold by both child value1 and child value2

14) Which of the following code could be used to compute the total number of bars sold by the

children?

A) for (int j=0; j<12; j++) sum += candy[j];

B) for (int j=0; j<12; j++) candy[j] = sum;

C) for (int j=0; j<12; j++) sum = candy[j];

D) for (int j=0; j<12; j++) sum += [j];

E) for (int j=0; j<12; j++) [j] += sum;

15) What does the following method do?

public int question15( )

{

int value1 = 0;

int value2 = 0;

for (int j = 0; j < 12; j++)

if (candy[j] > value1)

{

value1 = candy[j];

value2 = j;

}

return value2;

}

A) It returns the total number of candy bars sold

B) It returns the total number of children who sold 0 candy bars

C) It returns the total number of children who sold more than 0 candy bars

D) It returns the number of candy bars sold by the child who sold the most candy bars

E) It returns the index of the child who sold the most candy bars

16) We compare sorting algorithms by examining

A) the number of instructions executed by the sorting algorithm

B) the number of instructions in the algorithm itself (its length)

C) the types of loops used in the sorting algorithm

D) the amount of memory space required by the algorithm

E) whether the resulting array is completely sorted or only partially sorted

17) Both the Insertion Sort and the Selection Sort algorithms have efficiencies on the order of

________ where n is the number of values in the array being sorted.

A) n

B) n * log n

C) n2

D) n3

E) Insertion sort has an efficiency of n and Selection Sort has an efficiency of n2

18) Consider the array declaration and instantiation: int[ ] arr = new int[5]; Which of the

following is true about arr?

A) It stores 5 elements with legal indices between 1 and 5

B) It stores 5 elements with legal indices between 0 and 4

C) It stores 4 elements with legal indices between 1 and 4

D) It stores 6 elements with legal indices between 0 and 5

E) It stores 5 elements with legal indices between 0 and 5

19) If an int array is passed as a parameter to a method, which of the following would adequately

define the parameter list for the method header?

A) (int[ ])

B) (int a[ ])

C) (int[ ] a)

D) (int a)

E) (a[ ])

20) If int[ ] x = new int[15]; and the statement x[-1] = 0; is executed, then which of the following

Exceptions is thrown?

A) IndexOutOfBoundsException

B) ArrayIndexOutOfBoundsException

C) NegativeArraySizeException

D) NullPointException

E) ArithmeticException

21) Assume that BankAccount is a predefined class and that the declaration BankAccount[ ]

firstEmpireBank; has already been performed. Then the following instruction reserves memory

space for

firstEmpireBank = new BankAccount[1000];

A) a reference variable to the memory that stores all 1000 BankAccount entries

B) 1000 reference variables, each of which point to a single BankAccount entry

C) a single BankAccount entry

D) 1000 BankAccount entries

E) 1000 reference variables and 1000 BankAccount entries

22) The following code accomplishes which of the tasks written below? Assume list is an int

array that stores positive int values only.

int foo = 0;

for (int j =0 ; j < list.length; j++)

if (list[j] > foo) foo = list[j];

A) It stores the smallest value in list (the minimum) in foo

B) It stores the largest value in list (the maximum) in foo

C) It stores every value in list, one at a time, in foo, until the loop terminates

D) It counts the number of elements in list that are greater than foo

E) It counts the number of elements in list that are less than foo

23) If x is a char, and values is an int array, then values[x]

A) causes a syntax error

B) causes an Exception to be thrown

C) casts x as an int based on x’s position in the alphabet (for instance, if x is ‘a’ then it uses 0 and

if x is ‘z’ then it uses 25)

D) casts x as an int based on x’s ASCII value (for instance, if x is ‘a’ then it uses 97 and if x is ‘z’

then it uses 122)

E) casts x as an int based on the digit that is stored in x (for instance, if x is ‘3’ it uses 3) but

throws an exception if x does not store a digit

24) Given the following declarations, which of the following variables are arrays?

int[ ] a, b;

int c, d[ ];

A) a

B) a and b

C) a and d

D) a, b and d

E) a, b, c and d

25) If a and b are both int arrays, then a = b; will

A) create an alias

B) copy all elements of b into a

C) copy the 0th element of b into the 0th element of a

D) return true if each corresponding element of b is equal to each corresponding element of a

(that is, a[0] is equal to b[0], a[1] is equal to b[1] and so forth) and return false otherwise

E) return true if a and b are aliases and return false otherwise

26) The statement int[ ] list = {5, 10, 15, 20};

A) adds 4 int values to array list

B) initializes list to have 20 int values

C) initializes list to have 4 int values

D) declares list but does not initialize it

E) causes a syntax error because it does not include “new int[4]” prior to the list of values

27) To initialize a String array names to store the three Strings “Huey”, “Duey” and “Louie”, you

would do

A) String names = {“Huey”, “Duey”, “Louie”};

B) String[ ] names = {“Huey”, “Duey”, “Louie”};

C) String[ ] names = new String{“Huey”, “Duey”, “Louie”};

D) String names[3] = {“Huey”, “Duey”, “Louie”};

E) String names; names[0] = “Huey”; names[1] = “Duey”; names[2] = “Louie”;

28) A Polygon object in Java is

A) a shape defined as a collection of x, y points

B) a shape defined as a collection of lines

C) a shape defined as a collection of polylines

D) an array of shapes

E) 2 lines connected by 1 common point

29) Which of the following GUI components operates as a group so that only one of the options

can be selected at a time?

A) JCheckBox

B) JButton

C) JRadioButton

D) JButtonGroup

E) all of the above

30) To declare a three-dimensional int array called threeD, which of the following would you

use?

A) int[3] threeD;

B) int[ , , ] threeD;

C) int[ ][ ][ ] threeD;

D) int [ [ [ ] ] ] threeD;

E) int[ ] threeD[3];

31) A polyline in Java is

A) an object

B) a shape defined as a collection of lines

C) a shape defined as a collection of Polygons

D) an array of shapes

E) an shape defined by a collection of points

32) A Polygon object in Java can be

A) built up by using a sequence of addPoint method calls

B) defined by an array of x-y coordinates

C) defined by a polyline

D) A, B, and C all are true

E) only A and B are true

33) The Mouse Events include

A) mousePressed, mouseReleased, mouseClicked, mouseEntered, mouseExited

B) mousePressed, mouseReleased, mouseClicked, mouseEntered, mouseExited, mouseMoved,

mouseDragged

C) mousePressed, mouseReleased, mouseClicked, mouseMoved, mouseDragged

D) mouseClicked, mouseEntered, mouseExited, mouseMoved, mouseDragged

E) mouseMoved, mouseDragged

34) The Mouse Motion Events include

A) mousePressed, mouseReleased, mouseClicked, mouseEntered, mouseExited

B) mousePressed, mouseReleased, mouseClicked, mouseEntered, mouseExited, mouseMoved,

mouseDragged

C) mousePressed, mouseReleased, mouseClicked, mouseMoved, mouseDragged

D) mouseClicked, mouseEntered, mouseExited, mouseMoved, mouseDragged

E) mouseMoved, mouseDragged

35) The Key Events include

A) keyPressed, keyReleased

B) keyPressed, keyReleased, keyTyped

C) keyPressed, keyReleased, keyTyped, keyDown, keyUp

D) keyDown, keyUp, keyTyped

E) none of the above

36) As described in the Software Failure, a race condition bug in a computer program is one in

which

A) a race is held to see which team can finish a computer program first

B) two or more processes that start at the same time finish at different times

C) two or more processes race to create an error

D) two or more processes that share the same data continue running under wrong assumptions

after one of the processes changes the data

E) none of the above

1) Arrays have a built in toString method that returns all of the elements in the array as one

String with “\n” inserted between each element.

2) Java arrays can store primitive types and Strings, but cannot store any other type of Object

other than Strings.

3) A Java main method uses the parameter (String[ ] variable) so that a user can run the program

and supply “command-line” parameters. Since the parameter is a String array, however, the user

does not have to supply any parameters.

4) An array index cannot be a float, double, boolean or String.

5) If the following statement is performed: CD[ ] mycollection = new CD[200]; where CD is a

previously defined class, then mycollection[5] is a CD object.

6) It is possible to sort an array of int, float, double or String, but not an array of an Object class

such as a CD class.

7) To swap the 3rd and 4th elements in the int array values, you would do:

values[3] = values[4];

values[4] = values[3];

8) In Java, an array can only store one type of data. For instance, you cannot create an array that

stores both double and String values.

9) In a two-dimensional array, both dimensions must have the same number of elements, as

in[10][10].

10) An array, when instantiated, is fixed in size, but an ArrayList can dynamically change in size

when new elements are added to it.

11) Just as arrays can only have a fixed number of elements, set at the time the array is declared,

a parameter list also can only have a fixed number of elements, set at the time the method is

declared.

12) Although methods may be declared with a variable length parameter list, class constructors

cannot.

13) A ragged array is a multidimensional array whose initial indices don’t all start at zero.

14) So long as one is only accessing the elements of an ArrayList, its efficiency is about the

same as that of an array. It’s only when one begins to insert or remove elements towards the

front portion of an ArrayList that its efficiency deteriorates.

15) Mouse Events deal with detecting the actions of the buttons on a mouse, among other things,

while Mouse Motion Events deal with the movement of the mouse with/without buttons being

depressed.

16) Regarding the Software Failure: In the 2003 Northeast Blackout, the backup system crashed

for a different reason than the main system, which failed due to a race condition bug in the alarm

system software.

8.3 Free-Form Questions

1) Write a method to compute the average of an int array and return the value as a double. The

int array and the number of elements in the array are both passed as parameters to the method in

that order.

}

2) The length operator can be used to control a for-loop that iterates through each element of an

array, as in

for (int j=0; j<list.length; j++)

However, this is not necessarily safe. Why not?

3) Write a method to compute and return the value of max – min where max is the largest

element of an int array and min is the smallest element of an int array. The method is passed the

int array and an int value that denotes the number of elements in the array. You may assume that

the int array has at least 1 element in it.

4) Write code fragment to swap the two Strings stored by variables a and b.

5) The class Name consists of 4 instance data, String title, String first, String middle, String last.

The class has a constructor that is passed all 4 String values and initializes the class

appropriately, and has 4 methods, each returns one of the four instance data, called returnTitle( ),

returnFirst( ), returnMiddle( ) and returnLast( ). Name[ ] addressBook = new Name[100]; is

performed. Write a method that is passed 4 String parameters corresponding to a Name’s title,

first, middle, and last, and finds this Name in addressBook and returns the index of where this

Name was found, or -1 if the Name was not found. Assume that addressBook stores n entries (n

is an int).

}

6) Demonstrate how the following array is sorted using Insertion Sort. Show the array after each

pass of the outer loop.

[16, 3, 12, 13, 8, 1, 18, 9]

7) Demonstrate how the following array is sorted using Selection Sort. Show the array after each

pass of the outer loop.

[16, 3, 12, 13, 8, 1, 18, 9]

8) Write a code fragment to create a two-dimensional 10×10 array and initialize every element to

be the value of i * j where i and j are the two indices (for instance, element [5][3] is 5 * 3 = 15).

9) Explain how to alter the Selection Sort algorithm so that it sorts in descending order instead of

ascending order.

10) Write an insertion sort method to sort an array of String values (instead of an array of int

values). Assume the array is an instance data of the current class called list, and number is an int

instance data that stores the number of elements currently stored in list.

11) Write a method that takes an array of Strings as a parameter and the number of elements

currently stored in the array, and returns a single String that is the concatenation of all Strings in

the array.

}

12) Assume xArray and yArray are equal length arrays of int values storing num items (num is

also an int). Write a paint method for an Applet that will draw a Polygon shape using this

information. Assume xArray, yArray and num are all instance data of the Applet.

}

13) Write a method to output all elements of a two-dimensional array of int values as a table of

rows and columns. Use “\t” to get elements to line up properly. The method is passed the two-

dimensional array and two int values that denote the number of both dimensions (rows followed

by columns).

19

For the questions below, think of a GUI interface whereby a user can select between food items

and compute a total cost. The food items will be “Burger”, “Fries”, “Soda” and “Cookie”. A

“Burger” costs $2.00, “Fries” cost $1.25, “Soda” costs $1.00 and “Cookie” costs $.70. Assume

jcb1, jcb2, jcb3, jcb4 are JCheckBox elements declared to be private instance data of the GUI

class and jl1 and jl2 are JLabel elements declared to be private instance data of the GUI class.

14) Write code to create a JPanel with 4 JCheckBox GUI components and two JLabels for

output, one that says “Current cost is” and the other that outputs the computed cost based on

which of the food items has been selected.

15) Implement an ItemListener so that a new value is output by the second JLabel every time a

JCheckBox is clicked on.

16) In the RubberLinesPanel example in the text a single LineListener class was defined,

implementing both MouseListener and MouseMotionListener. What are the advantages and

disadvantages of this approach compared to defining two separate classes one for each kind of

Mouse Events?

17) Say that you want to construct a tiny drawing program, where the objects are defined using

line segments. One might use the rubber-banding ideas presented in this chapter to define the

endpoints of line segments, hooking them together into a polyline. One might provide a button

that turns a polyline into a polygon. If this approach is taken, what would be a good way to

represent the data involved in this program: the points, the line segments, the polylines, the

polygons?

18) Write a method public static int[ ][ ] matMult(int[ ][ ] x, int[ ][ ] y) which accepts two

matrices, x and y, and yields their product x * y as its result. Use the normal rules for matrix

multiplication. Be certain to test to see that x and y are compatible before beginning to compute

the matrix product.