Deck 6: More Conditionals and Loops

Question 1

Given the following switch statement where x is an int, answer the questions below
switch (x)
{
case 3 : x += 1;
case 4 : x += 2;
case 5 : x += 3;
case 6 : x++;
case 7 : x += 2;
case 8 : x--;
case 9 : x++
}
If x is currently equal to 5, what will the value of x be after the switch statement executes?

A) 8
B) 6
C) 11
D) 5
E) 10

Answer 1

C
Explanation: C) Since there are no break statements, the flow falls through any cases following the one that is True. The first case to be True is 5 since x is 5 prior to the switch statement. This changes x to 8, then to 9, then to 11, then to 10, and then finally back to 11.

Question 2

A continue statement

A) may be used within a while or a do-while loop, but not a for loop
B) is identical to a break statement within Java loops
C) may be used within any Java loop statement
D) may be used within a for loop, but not within a while or a do-while loop
E) none of the above

Answer 2

C
Explanation: C) Although use of continue statements should be avoided, if possible, they may be used within any of Java's three loops: for, while, and do-while.

Question 3

Given the following switch statement where x is an int, answer the questions below
switch (x)
{
case 3 : x += 1;
case 4 : x += 2;
case 5 : x += 3;
case 6 : x++;
case 7 : x += 2;
case 8 : x--;
case 9 : x++
}
The statement if (x < 0) y = x; else y = 0; can be rewritten using a conditional operator as

A) y = (x < 0) ? x : 0;
B) x = (x < 0) ? y : 0;
C) (x < 0) ? y = x : y = 0;
D) y = (x < 0);
E) y = if (x < 0) x : 0;

Answer 3

A
Explanation: A) The conditional operator of Java tests a condition, (x < 0) in this case, and if True, returns the value after the ? (x in this case) and if false, returns the value after the : (0 in this case). The original if statement is to assign y to x if (x < 0) and 0 otherwise. This will be accomplished by assigning y to be x or 0 based on (x < 0), as shown in A. In B, x is assigned the value of y or 0 which is backward. In C, the conditional operator is syntactically invalid. In D, y would be set to either True or false depending on (x < 0), and the statement in E is syntactically invalid.

Question 4

Given the following switch statement where x is an int, answer the questions below
switch (x)
{
case 3 : x += 1;
case 4 : x += 2;
case 5 : x += 3;
case 6 : x++;
case 7 : x += 2;
case 8 : x--;
case 9 : x++
}
If x is currently equal to 3, what will the value of x be after the switch statement executes?

A) 5
B) 6
C) 11
D) 10
E) 12

Question 5

A switch statement must have a default clause.

Question 6

The do loop differs from the while loop in that

A) the while loop will always execute the body of the loop at least once
B) the do loop will always execute the body of the loop at least once
C) the do loop will continue to loop while condition in the while statement is false and the while loop will continue to loop while the condition in the while statement is True
D) the while loop will continue to loop while condition in the while statement is false and the do loop will continue to loop while the condition in the while statement is True
E) none of the above, there is absolutely no difference between the two types of loops

Question 7

If a switch statement is written that contains no break statements whatsoever,

A) this is a syntax error and an appropriate error message will be generated
B) each of the case clauses will be executed every time the switch statement is encountered
C) this is equivalent to having the switch statement always take the default clause, if one is present
D) this is not an error, but nothing within the switch statement ever will be executed
E) none of the above

Question 8

The following nested loop structure will execute the inner most statement (x++) how many times?
For (int j = 0; j < 100; j++)
For (int k = 100; k > 0; k--)
X++;

A) 100
B) 200
C) 10,000
D) 20,000
E) 1,000,000

Question 9

Consider the following paint method to answer the questions below:
public void paint(Graphics page)
{
int x, y = 200;
page.setColor(Color.blue);
for (x = 100; x < 200; x += 20)
page.fillRect(x, y, 10, y-x);
}
This paint method will draw several bars (sort of like a bar graph). How many bars will be displayed?

A) 4
B) 5
C) 6
D) 10
E) 20

Question 10

Consider the following paint method to answer the questions below:
public void paint(Graphics page)
{
int x, y = 200;
page.setColor(Color.blue);
for (x = 100; x < 200; x += 20)
page.fillRect(x, y, 10, y-x);
}
Which of the following statements are True about Java loops?

A) all three loop statements are functionally equivalent
B) while loops and do loops are essentially the same; but while loops always execute at least once
C) if you know the number of times that a loop is to be performed, the best loop statement to use is a while loop
D) loops may be replaced by an appropriate combination of if-else and switch statements
E) none of the above

Question 11

Each case in a switch statement must terminate with a break statement.

Question 12

Consider the following paint method to answer the questions below:
public void paint(Graphics page)
{
int x, y = 200;
page.setColor(Color.blue);
for (x = 100; x < 200; x += 20)
page.fillRect(x, y, 10, y-x);
}
The size of each rectangle (bar)

A) increases in height while staying the same width
B) increases in width while staying the same height
C) increases in both width and height
D) stays the same size
E) decreases in height while staying the same width

Question 13

How many times will the following loop iterate?
Int x = 10;
Do {
System.out.println(x);
X--;
} while (x > 0);

A) 0 times
B) 1 time
C) 9 times
D) 10 times
E) 11 times

Question 14

Given that s is a String, what does the following loop do?
For (int j = s.length( ); j > 0; j--)
System.out.print(s.charAt(j-1));

A) it prints s out backwards
B) it prints s out forwards
C) it prints s out backwards after skipping the last character
D) it prints s out backwards but does not print the 0ᵗʰ character
E) it yields a run-time error because there is no character at s.charAt(j-1) for j = 0

Question 15

Control in a switch statement jumps to the first matching case.

Question 16

You might choose to use a switch statement instead of nested if-else statements if

A) the variable being tested might equal one of several hundred int values
B) the variable being tested might equal one of only a few int values
C) there are two or more int variables being tested, each of which could be one of several hundred values
D) there are two or more int variables being tested, each of which could be one of only a few values
E) none of the above, you would never choose to use a switch statement in place of nested if-else statements under any circumstance

Question 17

Given the following code, where x = 0, what is the resulting value of x after the for-loop terminates?
For (int i=0;i<5;i++)
X += i;

A) 0
B) 4
C) 5
D) 10
E) 15

Question 18

The following for-loop is an infinite loop.
for (int j = 0; j < 1000; ) i++;

Question 19

Consider the following paint method to answer the questions below:
public void paint(Graphics page)
{
int x, y = 200;
page.setColor(Color.blue);
for (x = 100; x < 200; x += 20)
page.fillRect(x, y, 10, y-x);
}
What will the following code do? Assume s is a String, x is an int initialized to 10, page is a Graphics object, and this is part of a paint method for an applet.
Boolean isVowel = false;
String vowels = "aeiou";
For (int j = 0; j < s.length( ); j++)
{
For (int k = 0; k < 5; k++)
If (s.charAt(j) == vowels.charAt(k)) isVowel = True;
If (isVowel) page.drawString(""+s.charAt(j), 10, 15*x++);
Else page.drawString(""+s.charAt(j), 110, 15*x++);
IsVowel = false;
}

A) The String s is printed down the applet in two columns, alternating each letter
B) The String s is printed across the applet with vowels printed in one row and all other characters printed in a row above the vowels
C) The String s is printed across the applet with vowels printed in one row and all other characters printed in a row below the vowels
D) The String s is printed down the applet in two columns with vowels appearing in the left column and all other characters in the right column
E) The String s is printed down the applet in two columns with vowels appearing in the right column and all other characters in the left column

Question 20

It is possible to convert any type of loop (while, do, or for) into any other.

Question 21

Rewrite the following nested if-else statement as an equivalent switch statement.
if (letter == 'A' | | letter == 'a') System.out.println("Excellent");
else if (letter == 'B' | | letter == 'b') System.out.println("You can do better");
else if (letter == 'C' | | letter == 'c') System.out.println("Try harder");
else if (letter == 'D' | | letter == 'd') System.out.println("Try much harder");
else System.out.println("Try another major! ");

Question 22

How many times will the System.out.println(*); statement execute inside of the following nested for-loops?
for (j=0; j<10; j++)
for (k=10;k>j;k--)
System.out.println("*");

Question 23

The following loop is syntactically valid.
for (int j = 0; j < 1000; j++) j--;

Question 24

Write a paint method to draw out an American flag. The flag will comprise a blue square in the upper left corner and 13 red and white stripes, starting with red, and alternating. 6 of the 13 stripes appear to the right of the blue square and the last 7 stripes appear beneath the blue square extending as far right as the other stripes. Use a for-loop to draw the stripes. Do not try to draw any stars in the blue square.

Question 25

The following for-loop is odd in that the loop increment value changes during iterations of the loop. Determine the number of times the loop iterates and the final value of j after the loop terminates.
int k = 0;
for (j = 0; j < 20; j += k)
k++;

Question 26

Write a set of code that outputs all of the int values between 1 and 100 with 5 values per line, and each of those 5 values spaced out equally. Use a single for-loop to solve this problem.

Question 27

A dialog box is a device which accepts voice commands.

Question 28

A data verification loop is a loop that asks the user to input a value within a restricted range repeatedly until the user has input a value within the requested range. Write a data verification loop that that inputs an int value x within the range 0 and 100. Assume cs1.Keyboard has been imported.

Question 29

Show the output that would occur from the following code, including proper spacing.
for (j = 0; j < 5; j++)
{
for (k = 0; k < 5; k++)
if (j!=k)
System.out.print(' ');
else
System.out.print('*');
System.out.println( );
}

Question 30

Rewrite the following if-else statement using a conditional operator.
if (x > y) z = x; else z = y;

Question 31

Write some code that inputs a set of int values and computes its average. Ask the user first how many int values will be input. Make sure that your code cannot produce a division by zero error. Assume that cs1.Keyboard has been imported.

Question 32

Given the following tax table information, write Java code to assign the double taxRate appropriately given the double pay. Select the selection statement (if, if-else, switch) that makes the most sense.
If pay is more than 100,000, tax rate is 40%
If pay is more than 60,000 and less than or equal to 100,000, tax rate is 30%
If pay is more than 30,000 and less than or equal to 60,000, tax rate is 20%
If pay is more than 15,000 and less than or equal to 30,000, tax rate is 10%
If pay is more than 5,000 and less than or equal to 15,000, tax rate is 5%
If pay is less than or equal to 5,000, tax rate is 0%

Question 33

In Java, it is possible to create an infinite loop out of while and do loops, but not for-loops.

Question 34

Describe a situation where you should use a do loop and a situation where you should use a while loop.

Question 35

The following code has a syntax error immediately before the word else. What is the error and why does it arise?
Fix the code so that this statement is a legal if-else statement.
if (x < 0) ; x++;
else x--;

Question 36

Write a "query-controlled" loop that will continue to input int values from the user, adding each to the int value sum, and then ask if the user has another value to input, until the user says that there are no more values. Assume that cs1.Keyboard has been imported.