Java Programming, 7th Edition Solutions manual and test bank Joyce Farrellg

Java Programming, 7th Edition Solutions manual and test bank Joyce Farrellg

Chapter 8: Arrays

TRUE/FALSE

1. You can declare an array variable by placing curly brackets after the array name.

ANS: F PTS: 1 REF: 398

2. When an application contains an array and you want to use every element of the array in some task, it is common to perform loops that vary the loop control variable from 0 to one less than the size of the array.

ANS: T PTS: 1 REF: 406

3. When you want to determine whether a variable holds one of many valid values, one option is to use a do…while loop to compare the variable to a series of valid values.

ANS: F PTS: 1 REF: 418

4. When using parallel arrays, if one array has many possible matches, it is most efficient to place the less common items first so that they are matched right away.

ANS: F PTS: 1 REF: 420

5. Many programmers feel that breaking out of a for loop early disrupts the loop flow and makes the code harder to understand.

ANS: T PTS: 1 REF: 421

6. When initializing an array, you must initialize all elements or none.

ANS: T PTS: 1 REF: 404

7. When you create an array variable, memory space is automatically reserved.

ANS: F PTS: 1 REF: 399

8. When array elements are passed by value, a copy of the value is made and used within the receiving method.

ANS: T PTS: 1 REF: 426-427

9. Since an array name is a reference, you are able to use the = operator for assigning and the == operator for comparisons.

ANS: F PTS: 1 REF: 427

10. When returning an array reference, square brackets are included with the return type in the method header.

ANS: T PTS: 1 REF: 429

MULTIPLE CHOICE

1. After you create an array variable, you still need to ____ memory space.

a.	create	c.	reserve
b.	organize	d.	dump

ANS: C PTS: 1 REF: 399

2. In Java, the size of an array ____ declared immediately following the array name.

a.	can be	c.	is never
b.	is always	d.	should be

ANS: C PTS: 1 REF: 399

3. Languages such as Visual Basic, BASIC, and COBOL use ____ to refer to individual array elements.

a.	( )	c.	{ }
b.	[ ]	d.	< >

ANS: A PTS: 1 REF: 399

4. A(n) ____ is an integer contained within square brackets that indicates one of an array’s variables.

a.	postscript	c.	variable header
b.	subscript	d.	indicator

ANS: B PTS: 1 REF: 399

5. When you declare an array name, no computer memory address is assigned to it. Instead, the array variable name has the special value ____, or Unicode value ‘\u0000’.

a.	empty	c.	false
b.	null	d.	zero

ANS: B PTS: 1 REF: 404

6. In Java, boolean array elements automatically are assigned the value ____.

a.	null	c.	true
b.	‘\u0000’	d.	false

ANS: D PTS: 1 REF: 404

7. When you create an array of objects, each reference is assigned the value ____.

a.	null	c.	true
b.	‘\u0000’	d.	false

ANS: A PTS: 1 REF: 404

8. You use a ____ following the closing brace of an array initialization list.

a.	.	c.	:
b.	;	d.	,

ANS: B PTS: 1 REF: 404

9. Providing values for all the elements in an array is called ____ the array.

a.	populating	c.	filling
b.	declaring	d.	irrigating

ANS: A PTS: 1 REF: 404

10. When any ____ type (boolean, char, byte, short, int, long, float, or double) is passed to a method, the value is passed.

a.	array	c.	element
b.	dummy	d.	primitive

ANS: D PTS: 1 REF: 427

11. The length ____ contains the number of elements in the array.

a.	box	c.	area
b.	field	d.	block

ANS: B PTS: 1 REF: 407

12. A(n) ____ loop allows you to cycle through an array without specifying the starting and ending points for the loop control variable.

a.	do…while	c.	enhanced for
b.	inner	d.	enhanced while

ANS: C PTS: 1 REF: 407

13. If a class has only a default constructor, you must call the constructor using the keyword ____ for each declared array element.

a.	default	c.	first
b.	new	d.	object

ANS: B PTS: 1 REF: 411

14. Comparing a variable to a list of values in an array is a process called ____ an array.

a.	validating	c.	checking
b.	using	d.	searching

ANS: D PTS: 1 REF: 418

15. A ____ array is one with the same number of elements as another, and for which the values in corresponding elements are related.

a.	cloned	c.	property
b.	parallel	d.	two-dimensional

ANS: B PTS: 1 REF: 419

16. When you initialize parallel arrays, it is convenient to use ____ so that the values that correspond to each other visually align on the screen or printed page.

a.	tabs	c.	spacing
b.	indentation	d.	dashes

ANS: C PTS: 1 REF: 420

17. When you perform a ____, you compare a value to the endpoints of numerical ranges to find the category in which a value belongs.

a.	range match	c.	reference
b.	sort	d.	search

ANS: A PTS: 1 REF: 422

18. It is a good programming practice to ensure that a subscript to an array does not fall below zero, causing a(n) ____.

a.	array dump	c.	conundrum
b.	runtime error	d.	compiling error

ANS: B PTS: 1 REF: 423

19. Individual array elements are ____ by value when a copy of the value is made and used within the receiving method.

a.	sorted	c.	received
b.	passed	d.	stored

ANS: B PTS: 1 REF: 426-427

20. Primitive type variables are always passed by ____.

a.	value	c.	location
b.	reference	d.	memory

ANS: A PTS: 1 REF: 428

21. When a method returns an array reference, you include ____ with the return type in the method header.

a.	{ }	c.	< >
b.	( )	d.	[ ]

ANS: D PTS: 1 REF: 429

22. Which of the following println statements will display the last myScores element in an array of 10?

a.	System.out.println(vals[0]);	c.	System.out.println(vals[9]);
b.	System.out.println(vals[1]);	d.	System.out.println(vals[10]);

ANS: C PTS: 1 REF: 400

23. Which of the following statements correctly declares and creates an array to hold five double scores values?

a.	integer[] scores = new double[5]	c.	double[] = new scores[5]
b.	double[] scores = new integer[5]	d.	double[] scores = new double[5]

ANS: D PTS: 1 REF: 400

24. Which of the following statements correctly initializes an array with an initialization list?

a.	int[] nums = {2, 4, 8};	c.	int nums = [2, 4, 8];
b.	int[] nums = (2, 4, 8);	d.	int nums() = int{2, 4, 8}

ANS: A PTS: 1 REF: 404

25. In which of the following statements is the value of myVals null?

a.	int myVals = ""	c.	myVals = int[null]
b.	int [] myVals;	d.	int[null] = myVals

ANS: B PTS: 1 REF: 404

COMPLETION

1. A(n) ____________________ is a named list of data items that all have the same type.

ANS: array

PTS: 1 REF: 398

2. When you declare or access an array, you can use any expression to represent the size, as long as the expression is a(n) ____________________.

ANS: integer

PTS: 1 REF: 400

3. When you declare int[] someNums = new int[10];, each element of someNums has a value of ____________________ because someNums is a numeric array.

ANS:

0

zero

PTS: 1 REF: 404

4. An instance variable or object field is also called a(n) ____________________ of the object.

ANS: property

PTS: 1 REF: 407

5. When any primitive type is passed to a method, the ____________________ is passed.

ANS: value

PTS: 1 REF: 427

MATCHING

Match each term with the correct statement below.

a.	array variable	f.	length
b.	reference type	g.	foreach loop
c.	elements	h.	reference types
d.	int	i.	return
e.	Java object names

1. Numbered beginning with 0

2. An array field

3. An enhanced for loop

4. Declared in the same way you declare any simple variable

5. A nonprimitive object

6. A primitive type

7. Represent computer memory addresses

8. A statement used to return an array from a method

9. Hold memory addresses where values are stored

1. ANS: C PTS: 1 REF: 399

2. ANS: F PTS: 1 REF: 407

3. ANS: G PTS: 1 REF: 408

4. ANS: A PTS: 1 REF: 398

5. ANS: B PTS: 1 REF: 427

6. ANS: D PTS: 1 REF: 427

7. ANS: E PTS: 1 REF: 403

8. ANS: I PTS: 1 REF: 429

9. ANS: H PTS: 1 REF: 427

SHORT ANSWER

1. Describe a situation in which storing just one value at a time in memory does not meet your needs.

ANS:

At times you might encounter situations in which storing just one value at a time in memory does not meet your needs. For example, a sales manager who supervises 20 employees might want to determine whether each employee has produced sales above or below the average amount. When you enter the first employee’s sales value into an application, you can’t determine whether it is above or below average because you don’t know the average until you have all 20 values. Unfortunately, if you attempt to assign 20 sales values to the same variable, when you assign the value for the second employee, it replaces the value for the first employee.

PTS: 1 REF: 398

2. What is a subscript and how are the array’s elements numbered?

ANS:

A subscript is an integer contained within square brackets that indicates one of an array’s variables, or elements. In Java, any array’s elements are numbered beginning with 0, so you can legally use any subscript from 0 to 19 when working with an array that has 20 elements.

PTS: 1 REF: 399

3. What does an array’s name represent and what value does it hold when declared?

ANS:

Array names represent computer memory addresses; that is, array names contain references, as do all Java objects. When you declare an array name, no computer memory address is assigned to it. Instead, the array variable name has the special value null, or Unicode value ‘\u0000’. When you declare int[] someNums;, the variable someNums has a value of null.

PTS: 1 REF: 404

4. When working with arrays, why is it beneficial to use a loop with a declared symbolic constant equal to the size of the array?

ANS:

It is convenient to declare a symbolic constant equal to the size of the array and use the symbolic constant as a limiting value in every loop that processes the array. That way, if the array size changes in the future, you need to modify only the value stored in the symbolic constant, and you do not need to search for and modify the limiting value in every loop that processes the array.

PTS: 1 REF: 407

5. When using an array with all elements used, why would a programmer use a loop control variable from 0 to one less than the size of the array? Give an example.

ANS:

When an application contains an array and you want to use every element of the array in some task, it is common to perform loops that vary the loop control variable from 0 to one less than the size of the array. For example, if you get input values for the elements in the array, alter every value in the array, sum all the values in the array, or display every element in the array, you need to perform a loop that executes the same number of times as there are elements.

PTS: 1 REF: 406

6. How would you use a method that belongs to an object that is part of the array? Use an example and demonstrate with Java code.

ANS:

To use a method that belongs to an object that is part of an array, you insert the appropriate subscript notation after the array name and before the dot that precedes the method name. For example, to print data for seven Employees stored in the emp array, you can write the following:

for(int x = 0; x < NUM_EMPLOYEES; ++x)

System.out.println (emp[x].getEmpNum() + " " + emp[x].getSalary());

PTS: 1 REF: 411

7. Why would you use spacing when initializing parallel arrays?

ANS:

When you initialize parallel arrays, it is convenient to use spacing so that the values that correspond to each other visually align on the screen or printed page.

PTS: 1 REF: 420

8. How would a programmer perform a range match when writing an application that takes into consideration different discount rates for customers? Give an example.

ANS:

Create two corresponding arrays and perform a range match, in which you compare a value to the endpoints of numerical ranges to find the category in which a value belongs. For example, one array can hold the five discount rates, and the other array can hold five discount range limits. If you only use the first figure in each range, you can create an array that holds five low limits:

int[] discountRangeLimit= {1, 13, 50, 100, 200};

A parallel array can hold the five discount rates:

double[] discountRate = {0, 0.10, 0.14, 0.18, 0.20};

Then, starting at the last discountRangeLimit array element, for any numOfItems greater than or equal to discountRangeLimit[4], the appropriate discount is discount[4]. In other words, for any numOrdered less than discountRangeLimit[4], you should decrement the subscript and look in a lower range.

PTS: 1 REF: 422

9. What is different about passing an array to a method rather than passing a primitive type to a method?

ANS:

The outcome is quite different when you pass an array (that is, pass its name) to a method. Arrays, like all nonprimitive objects, are reference types; this means that the object actually holds a memory address where the values are stored and the receiving method gets a copy of the array’s actual memory address. Therefore, the receiving method has access to, and the ability to alter, the original values in the array elements in the calling method.

PTS: 1 REF: 426-427

10. How can you use the enhanced for loop?

ANS:

You can use the enhanced for loop to cycle through an array of objects. For example, to display data for seven Employees stored in the emp array, you can write the following:

for(Employee worker : emp)

System.out.println(worker.getEmpNum() + " " + worker.getSalary();

In this loop, worker is a local variable that represents each element of emp in turn. Using the enhanced for loop eliminates the need to use a limiting value for the loop and eliminates the need for a subscript following each element.

PTS: 1 REF: 412

11. When populating an array with an initialization list, you do not need to use the new keyword or provide an array size. Explain why this is the case.

ANS:

When you populate an array upon creation by providing an initialization list, you do not

give the array a size because the size is assigned based on the number of values you place in the initializing list. Also, when you initialize an array, you do not need to use the keyword new. New memory is assigned based on the length of the list of provided values.

PTS: 1 REF: 404

12. Why is the length field a good option when writing a loop that manipulates an array? What programming error is common when attempting to use length as an array method?

ANS:

You can use a field (instance variable) that is automatically assigned a value for every array you create. The length field contains the number of elements in the array. Later, if you modify the size of the array and recompile the program, the value in the length field of the array changes appropriately. When you work with array elements, it is always better to use a symbolic constant or the length field when writing a loop that manipulates an array.

A frequent programmer error is to attempt to use length as an array method, referring to

xxx.length(). However, length is not an array method; it is a field. An instance

variable or object field such as length is also called a property of the object.

PTS: 1 REF: 407

13. While you can provide any legal identifier you want for an array, conventional rules are typically followed. List and describe the naming conventions for naming arrays.

ANS:

Java programmers conventionally name arrays by following the same rules they use for variables:

Array names start with a lowercase letter.

Use uppercase letters to begin subsequent words.

Additionally, many programmers observe one of the following conventions to make it

more obvious that the name represents a group of items:

Arrays are often named using a plural noun such as studentScores.

Arrays are often named by adding a final word that implies a group, such as salesList.

PTS: 1 REF: 398-399

14. int[] sixNumbers = {1, 2, 3, 4};

The above code creates an array named sixNumbers. Describe how array sizes are determined when using an initialization list and how memory is assigned.

ANS:

When you populate an array upon creation by providing an initialization list, you do not give the array a size—the size is assigned based on the number of values you place in the initializing list. For example, the sixNumbers array in the sample code has a size of 4. Also, when you initialize an array, you do not need to use the keyword new because new memory is assigned based on the length of the list of provided values. In Java, you cannot directly initialize part of an array. For example, you cannot create an array of 10 elements and initialize only five; you must initialize either every element or none of them.

PTS: 1 REF: 404

15. The following statement declares an array:

int[] increaseValues = new int[5]

final int PLUSTWO = 2;

Create a loop that will add 2 to every array element. Use a symbolic constant named PLUSTWO and use the length field in the loop that will contain the number of elements in the array.

ANS:

for(counter = 0; counter < increaseValues.length; ++counter)

increaseValues[counter] += PLUSTWO;

PTS: 1 REF: 406-407

CASE

1. public class CostArray

{

public static void main(String[] args)

{

double[] costs = new double[3];

costs[0] = 5.00;

costs[1] = 7.00;

costs[2] = 9.00;

System.out.println(costs[3]);

}

}

Once the above code is compiled and executed, an error message is generated. Explain the error message that will result and explain the reason for the error.

ANS:

An out-of-bounds error is generated when the code is compiled and executed. The last executable line in the code is an output statement that attempts to display a costs value using a subscript that is beyond the range of the array: System.out.println(costs[3]). The program will run successfully when the subscript used with the array is 0, 1, or 2. However, when the subscript reaches 3, the ArrayIndexOutOfBoundsException error is generated. The message indicates that the subscript is out of bounds and that the offending index is 3.

PTS: 1 REF: 403

2. String[] countyNames = {"Clark", "Delaware", "Madison"};

Using the above statement, what will be the value of countyNames[0], countyNames[1], and countyNames[2]?

ANS:

countyNames[0] will hold the value “Clark”

countyNames[1] will hold the value “Delaware”

countyNames[2] will hold the value “Madison”

PTS: 1 REF: 412

3. Write the statement to create an array named studentScores that will store five integer value student scores. Initialize the array using an initialization list with the values 70, 85, 92, 67, and 76.

ANS:

int[] studentScores = {70, 85, 92, 67, 76};

PTS: 1 REF: 404

4. Using just one statement, declare and create an array that will reserve memory locations for 10 scores values that are type double.

ANS:

double[] scores = new double[10];

PTS: 1 REF: 399

5. Write the statement to declare an array of integers that will hold studentScores.

ANS:

int[] studentScores;

PTS: 1 REF: 398

6. double[] studentScores;

double studentScores[];

Are both of the above statements valid for declaring an array variable? Why or why not?

ANS:

You declare an array variable in the same way you declare any simple variable, but you insert a pair of square brackets after the type. To declare an array of double values to hold studentScores, you can write the following:

double[] studentScores;

In Java, you can also declare an array variable by placing the square brackets after the array name, as in double studentScores[];. This format is familiar to C and C++ programmers, but the preferred format among Java programmers is to place the brackets following the variable type and before the variable name.

PTS: 1 REF: 398

7. String[] countyNames = {"Clark", "Delaware", "Madison"};

What will be the value of countyNames[0].length(), countyNames[1].length(), and countyNames[2].length()?

ANS:

countyNames[0].length() will have a value of 5

countyNames[1].length() will have a value of 8

countyNames[2].length() will have a value of 7

PTS: 1 REF: 407

8. public static int[] sampleArray()

{

int studentScores = {72, 91, 83};

____

}

Using the above code, write the statement that will return the array name.

ANS:

return studentScores;

PTS: 1 REF: 429

9. Write the statement to declare an array variable named studentScores with type double. Write a second statement to create an array of 10 objects.

ANS:

double[] studentScores;

studentScores = new double [10];

PTS: 1 REF: 399

10. double[] studentScores = new double[3];

studentScores[0] = 93;

studentScores[1] = 77;

studentScores[2] = 85;

Write a println statement to display the last element of the studentScores array.

ANS:

System.out.println(studentScores[2]);

PTS: 1 REF: 399-400