Deck 16: RGB Colors, Decimal Conversion, Java Naming, and Random Number Generation

Question 1

In the RGB color system, there are 256 possible values for each color (red, green, and blue). A color is considered gray when its red, green, and blue values are identical. There are __________ shades of gray (excluding black and white).

Answer 1

254

Question 2

Convert the following numbers to decimal: 0010 1010 (binary) and 2B (hexadecimal).

Answer 2

0010 1010 = 42 ( = 32 + 8 + 2 ) and 2B = 43 ( = 32 + 11)

Question 3

Give the 4-digit hexadecimal Unicode value for the character '&'. (You can refer to Appendix C.)

Answer 3

0026

Question 4

In the RGB color system, there are 256 possible values for each color (red, green, and blue). How many possible colors are there?

Question 5

Write a statement to define each of the following variables using Java naming conventions:
A. A variable named percent that holds the value .023
B. A constant that will hold the number of inches in a foot (12 ).
C. A single character that stores the letter A.

Question 6

Consider the following source code. What should you name the save file for this source code?
public class SpringBreak
{
// lots of code here
}

Question 7

Where is the error in the following code sequence, and why? How would you correct it?
float number = 6;
double d = number;
number = 19.7;

Question 8

Write a Java statement to calculate the value of this formula. Assume that z, x and n are ints and have been assigned values. Assign the result to a variable of the appropriate type.
_____
√ 3z + x
4 - xⁿ

Question 9

Write Java statements to instantiate a random number generator object and generate a random integer between 100 and 250 (inclusive).

Question 10

Complete this code in main to perform the requested operations for a date entered by the user in this format: month dd, yyyy.
public static void main( String [] args )
{
Scanner scan = new Scanner( System.in );
System.out.print( "Enter a date > " );
String date = scan.nextLine( );
Output the first letter in the month.
Output the date in all lowercase letters.
Output the year portion of the date-that is, the characters in the date that follow the comma. For example, if the date is February 24, 2016, you would output 2016. (Note: Your code should work for ANY date in that format.)

Question 11

Convert the String input below to a double and display 5 times that value. Do not hard code either 12.4 or 62.0; assume that you do not know the value of input.
String input = "12.4";

Question 12

If you want to use the Random class in your program, what statement must you have at the beginning of your program? Import only the Random class.

Question 13

A String variable named s has been declared and holds some value. Output the number of characters in s.

Question 14

A String variable named email contains the email of a person in this format: [e-mail]. Examples are [e-mail] and [e-mail]. For simplicity, assume that there is exactly one @ character and one . (dot) character in the String email, and that the @ character is before the . (dot) character.
Output the username, the service provider, and the extension of email.

Question 15

Complete the code, changing the fill color of the GraphicsContext reference gc to a color with red = 100, green = 200, and blue = 60.
// gc is a GraphicsContext reference
// your code goes here

Question 16

Complete the code, drawing a line between points (100, 200) and (34, 67).
// gc is a GraphicsContext reference
// your code goes here

Question 17

Complete the code, drawing a rectangle (with the current color, whatever it is) so that the coordinates of its upper left corner are (100, 200) and the coordinates of its bottom right corner are (175, 225).
// gc is a GraphicsContext reference
// your code goes here

Question 18

Complete the code, drawing two non-solid concentric circles (with the current fill color, whatever it is) so that their diameters are 200 and 100 and the coordinates of their center are (250, 150).
// gc is a GraphicsContext reference
// your code goes here

Question 19

Complete the code, drawing three more lines using the current stroke color to complete a square between the points (100, 100) and (300, 300).
// gc is a GraphicsContext reference
gc.strokeLine( 100, 100, 300, 100 );
// your code goes here

Question 20

Complete the code, drawing a triangle whose edges are blue and whose vertices are the points (100, 125), (150, 200), and (100, 300).
// gc is a GraphicsContext reference
// your code goes here

Question 21

Complete the code, drawing a solid cyan figure with its vertices at the points (100, 125), (150, 200), (100, 300), and (350, 350); note that the Color class includes a constant for cyan.
// gc is a GraphicsContext reference
// your code goes here

Question 22

Complete this code. Assume that you have created a budget and have set your maximum daily spending to $30. Assume that the appropriate classes have been imported.
public static void main( String [] args )
{
//***** 1. define the maximum daily budget as a constant
//***** 2. Instantiate (create) a Scanner object.
//***** 3. Input the amount actually spent today.
//***** 4. Using an if/else statement, tell the user how their
// actual spending compares with their maximum daily budget
// (more, less, or the same?)
}

Question 23

A String variable named s has been declared and holds some value. If its number of characters is even and greater than or equal to 10, output EVEN AND LONG, otherwise, output ODD OR SHORT.

Question 24

Assume that we have already declared an int named number and a char named letter. We want to assign a boolean value to a variable named result1 such that if number is equal to 100 and letter is equal to A, then result1 is true; otherwise, result1 is false.
boolean result1;
// your code goes here

Question 25

Assume that we have already declared a String named email. We want to assign a boolean value to a variable named result2 such that if email has 10 characters or more and its first character is A, then result2 is true; otherwise, result2 is false.
boolean result2;
// your code goes here

Question 26

Write a complete program. Prompt the user for two integers (using Scanner). Assume that the user will enter two well-formatted integers. You do not have to check for that. They should both be greater than or equal to 0 and the first one must be strictly less than the second one; if this is not the case, output WRONG DATA. If that is the case, calculate the exact ratio of the first number divided by the second number (for example, if the numbers are 6 and 10, the ratio is 0.6; if the numbers are 4 and 10, the ratio is 0.4). If that ratio is strictly greater than 0.5, output ABOVE AVERAGE; if it is equal to 0.5 (do not worry about possible rounding errors), output AVERAGE; if it is less than 0.5, output BELOW AVERAGE.

Question 27

A String variable named s has been declared and holds some value. If s contains the String MIDTERM or FINAL, output EXAM; otherwise, output LECTURE.

Question 28

Assuming a and b are int variables, apply one of DeMorgan's laws to create an equivalent expression for the following boolean expression:
!( a > 8 && b < 19 )

Question 29

Write a loop to output the word EXAM 99 times.

Question 30

Write a loop to calculate the total of all the numbers between 100 and 200 included (i.e., 100 + 101 + … + 199 + 200); output the total.

Question 31

Inside the main method, prompt the user to enter a word that contains a Z until the user enters one.

Question 32

Inside the main method, prompt the user to enter a word that has at least five characters until the user does. After that, count how many times the letter A is in that word and output the result.
Example 1:
Enter a word > Helo
Enter a word > BLABLA
Number of As is 2
Example 2:
Enter a word > Hi
Enter a word > Mid
Enter a word > PROGRAMMINGEXAMJAVA
Number of As is 4

Question 33

The class Ticket has been coded as follows. Write the mutators (setPrice and setService methods) for the Ticket class. The price must be greater than or equal to 0. The service must be either A or B; the default service is B.
public class Ticket
{
private double price;
private char service;
public Ticket( double newPrice, char newService )
{
setPrice( newPrice );
setService( newService );
}
}

Question 34

The class Ticket has been coded as follows. Write the accessor (getPrice and getService methods) for the Ticket class.
public class Ticket
{
private double price;
private char service;
public Ticket( double newPrice, char newService )
{
setPrice( newPrice );
setService( newService );
}
}

Question 35

The class Ticket has been coded as follows. Code a method that switches the value of service: if it is A, it changes to B; if it is B, it changes to A.
public class Ticket
{
private double price;
private char service;
public Ticket( double newPrice, char newService )
{
setPrice( newPrice );
setService( newService );
}
}

Question 36

The class Ticket has been coded as follows. Code the toString method so it returns the service and price separated by a : (colon) as in the following examples:
Example 1: B:34.99
Example 2: A:94.99
Example 3: B:44.99
public class Ticket
{
private double price;
private char service;
public Ticket( double newPrice, char newService )
{
setPrice( newPrice );
setService( newService );
}
}

Question 37

The class Ticket has been coded as follows:
public class Ticket
{
private double price;
private char service;
public Ticket( double newPrice, char newService )
{
setPrice( newPrice );
setService( newService );
}
}
What is the data type of the parameter and the return type of the tax method?
public double tax( float rate )

Question 38

The class Ticket has been coded as follows:
public class Ticket
{
private double price;
private char service;
public Ticket( double newPrice, char newService )
{
setPrice( newPrice );
setService( newService );
}
}
In a client class and inside the main method, myTicket is an object reference of type Ticket. Call the method tax with myTicket, assuming a tax rate of 0.06, and assign the resulting tax value to a variable named myTax.
float taxRate = 0.06f;
// Your code goes here

Question 39

The class Ticket has been coded as follows:
public class Ticket
{
private double price;
private char service;
public Ticket( double newPrice, char newService )
{
setPrice( newPrice );
setService( newService );
}
}
Consider the following constant of class Ticket:
public static char DEFAULT_SERVICE = 'B';
In a client class and inside main, write a statement to output the value of the above constant.

Question 40

Convert 403 into a binary number, and then into a hexadecimal number.

Question 41

List three programming languages and an application for each.

Question 42

What is a LAN, and what is its purpose?

Question 43

Identify the error in this shortcut operator: a + = 2;

Question 44

What is the maximum length of an identifier?

Question 45

How would you determine which integer data type would be best to use?

Question 46

Why will there be zero iterations of the while loop if the loop condition is false the first time it is evaluated?

Question 47

Identify whether each of the following problems is a result of a missing priming read or missing update read.
A. The first time the while loop condition is evaluated, the result is unpredictable.
B. When the sentinel value is read and processed, it produces incorrect results.
C. The while loop continuously processes the same data item, leading to an endless loop.

Question 48

If an int instance variable has an initial value of 10, what can you infer about the constructor for that value?

Question 49

Place the following steps required to calculate a minimum value in the correct order.
-Assume the first value read is the minimum.

Question 50

Place the following steps required to calculate a minimum value in the correct order.
-Identify a new current minimum if its value is less than previous minimum.

Question 51

Place the following steps required to calculate a minimum value in the correct order.
-Compare a value to the current minimum.

Question 52

Give the values that are assigned to each variable after the statements below are executed.
-int a = 5 / 3; __________

Question 53

Give the values that are assigned to each variable after the statements below are executed.
-int b = 8 % 3; __________

Question 54

Give the values that are assigned to each variable after the statements below are executed.
-double c = 3 / 7; __________

Question 55

Give the values that are assigned to each variable after the statements below are executed.
-double d = 10.0 / 3; __________

Question 56

Give the values that are assigned to each variable after the statements below are executed.
-int e = 5 + 10 / 3; __________

Question 57

Give the values that are assigned to each variable after the statements below are executed.
-int f = 3; f += 10; __________

Question 58

Give the values that are assigned to each variable after the statements below are executed.
-int h = 5 + 10 * 3; _________+

Question 59

Give the values that are assigned to each variable after the statements below are executed.
-double i = ( double ) ( 6 / 4 ); __________

Question 60

In the RGB color system, there are 256 possible values for each color (red, green, and blue); a color is considered gray when its red, green, and blue values are identical. How many shades of gray are there (excluding black and white)?

Question 61

Where is the error in the following code sequence, and why? How would you correct it?
int number = 6;
double d = number;
number = 19.0;

Question 62

Convert the String input below to an int and display 4 times that value. Do not hard code either 7 or 28; assume that you do not know the value of input.
String input = "7";

Question 63

Complete the code, drawing a solid circle (with the current fill color, whatever it is) so that its diameter is 200 and the coordinates of its center are (250, 150).
// gc is a GraphicsContext reference
// your code goes here

Question 64

Assuming a is an int variable and flag is a boolean variable, apply one of DeMorgan's laws to create an equivalent expression for the following boolean expression:
!( a == 100 || flag == false )

Question 65

A String variable named s has been declared and holds some value. If its number of characters is even, output EVEN; otherwise, output ODD.

Question 66

Inside the main method, prompt the user to enter a word that does not contain a Y until the user enters one.

Question 67

Write a loop to output the word "FINAL" 25 times.

Question 68

Consider the following class:
public class Radio
{
private double frequency;
private String name;
// overloaded constructor
// accessors (get methods)
// mutators (set methods)
// other methods
}
Code the two mutators. Frequency must be between 80 and 110 included. If the parameter is out of that range, set the frequency to 100. There is no constraint on name. The mutators should return the Radio reference that calls them.
// Your code goes here

Question 69

Consider the following class:
public class Radio
{
private double frequency;
private String name;
// overloaded constructor
// accessors (get methods)
// mutators (set methods)
// other methods
}
Code the overloaded constructor. Call the mutators (set methods) to enforce constraints. Assume that they have been coded correctly.
// Your code goes here

Question 70

Write the code to compute and output how many times the value 99 is found in an array of integers named numbers.

Question 71

An array, numbers, has been declared and initialized as follows:
int [ ] numbers = { 45, 78, 99, 12, 66 };
What is the index of 78?
What is the array element at index 4?
Change the array so that we have value 77 instead of 99.
Swap the value at indexes 1 and 2 without knowing what the values are.
Using a loop, assume that you do not know how many elements are in the array and increase all the values of numbers by 10.
Using a loop, assume that you do not know how many elements are in the array and what they are, and calculate and output the number of elements that are strictly greater than 50.
Using a loop, assume that you do not know how many elements are in the array and output every other element of the array, starting at the first element.

Question 72

An array, letters, has been declared and initialized as follows:
char [ ] letters = { 'A', 'B', 'A', 'C', 'E', 'D' };
What is the index of C?
What is the array element at index 1?
Swap the value at indexes 3 and 5 (C and D) without knowing what the values are. After the swap, the array will look like A B A D E C.
Using a loop, assume that you do not know how many elements are in the array and the contents of the array, and compute and output how many As are in the array letters.
Using a loop, assume that you do not know how many elements are in the array and the contents of the array, and change all the As of letters into Zs; do not change the other letters.

Question 73

Code a method that returns an int array that is parallel to its array parameter letters. If an element of letters is A, the corresponding element of the returned array is 1; otherwise, it is 0.
Example 1: If the array parameter is A B A, the returned array is 1 0 1.
Example 2: If the array parameter is A B A C D A A, the returned array is 1 0 1 0 0 1 1.
Example 3: If the array parameter is A A E F G, the returned array is 1 1 0 0 0.
public static int [ ] convert( char [ ] letters )
{
// Your code goes here
}

Question 74

Here is the code for selection sort (for an array of ints):
public static void selectionSort( int [ ] arr )
{
int temp;
int max;
for ( int i = 0; i < arr.length - 1; i++ )
{
max = indexOfLargestElement( arr, arr.length - i );
System.out.println( "max = " + max );
temp = arr[max];
arr[max] = arr[arr.length - i - 1];
arr[arr.length - i - 1] = temp;
}
}
public static int indexOfLargestElement( int [ ] arr, int size )
{
int index = 0;
for ( int i = 1; i < size; i++ )
{
if ( arr[i] > arr[index] )
index = i;
}
return index;
}
We are running the following code:
int [ ] numbers = { 10, 6, 4, 8 };
selectionSort( numbers );
Show what the output statement in the selectionSort method outputs. The question is not what the array looks like at the end; we know it is sorted in ascending order.

Question 75

Consider the following two-dimensional array:
String [ ][ ] states = { { "CA", "CO" },
{ "MD", "IL", "ME", "MI" }, { "NY", "NJ", "NE" } };
What is the value of states[2][1]?
Retrieve ME from the array states and assign it to a String variable of your choice.
Using a loop, output all the states that start with the letter M in the second row (as in this example).
Assume that you do not know how many columns are in the second row, i.e., do not hard code 4. Assume that you do not know that the three states are MD, ME, and MI.

Question 76

The variable cities is an ArrayList of type String, Write the code to output all its elements.

Question 77

The variable numbers is a two-dimensional array of type int. Output all of its elements that are strictly greater than 10.

Question 78

The ArrayList method trimToSize has the following API:
public void trimToSize( )
It trims the capacity of this ArrayList instance to be the list's current size.
ArrayList numbers = new ArrayList( );
numbers.add( 32 );
numbers.add( 17 );
numbers.add( 6 );
Use trimToSize to trim the capacity of numbers to its current size:

Question 79

The ArrayList method indexOf has the following API:
public int indexOf( HYPERLINK "http://docs.oracle.com/javase/7/docs/api/java/lang/Object.html" \o "class in java.lang" Object o)
Return the index of the first occurrence of o in this list or -1 if this list does not contain o.
ArrayList cities = new ArrayList( );
cities.add( "Baltimore" );
// more statements adding cities to the ArrayList cities
Use indexOf to retrieve the index of the city New York in cities (it may or may not be there) and assign the result to a variable of your choice.

Question 80

Class Reply inherits from class Post. Write the header for class Reply (one line only).