Deck 4: Conditionals and Loops

Question 1

The ___________________ statement causes execution of a loop to stop, and the statement following the loop to be subsequently executed.

A) stop
B) halt
C) continue
D) break
E) switch

Answer 1

D
Explanation: The break statement causes the execution of a loop to stop, and the statements to be subsequently executed. Therefore choice d is correct. The continue statement causes current iteration of a loop to stop and the condition to be evaluated again, either stopping the loop or causing the next iteration. There are no stop or halt statements in the Java language. A switch statement is a control structure.

Question 2

A _________________ is an object that has methods that allow you to process a collection of items one at a time.

A) iterator
B) loop
C) conditional
D) palindrome
E) nested loop

Answer 2

A
Explanation: An iterator is an object that has methods that allow you to process a collection of items one at a time. None of the other choices are objects in Java.

Question 3

Which of the following for loop headers will cause the body of the loop to be executed 10 times?

A) for(int i = 0; i <= 10; i++)
B) for(int i = 1; i < 10; i++)
C) for(int i = 1; i <= 11; i++)
D) for(int i = 0; i < 10; i++)
E) none of these for loops will execute the loop body 10 times

Answer 3

D
Explanation: The loop executes when i is equal to 0, 1, 2, 3, 4, 5, 6, 7, 8, and 9. Therefore it executes exactly 10 times. Choice a and c execute 11 times, while choice a executes 9 times.

Question 4

In a nested if statement an else clause is matched to the closest unmatched if.

Question 5

Which of the following expressions best represents the condition "if the grade is between 70 and 100"?

A) if (75 < grade && grade < 100)
B) if (grade != 75 && grade != 100)
C) if (75 < grade < 100)
D) if (75 > grade || grade < 100)
E) if (75 < grade || grade < 100)

Question 6

Let a and b be valid boolean expressions. Which of the following best describes the result of the expression a || b?

A) It will evaluate to true if a evaluates to true and b evaluates to true. It will evaluate to false otherwise.
B) It will evaluate to false if a evaluates to false and b evaluates to false. It will evaluate to true otherwise.
C) It will evaluate to true if a evaluates to false and b evaluates to false. It will evaluate to true otherwise.
D) It will evaluate to true if a evaluates to false or b evaluates to false. It will evaluate to true otherwise.
E) None of the above statements correctly describes the evaluation of the expression.

Question 7

Suppose we wanted to process a text file called "input.txt" using the Scanner object. Which of the following lines of code correctly creates the necessary Scanner object?

A) Scanner inputFile = new Scanner("input.txt");
B) Scanner inputFile = new Scanner(new InputFile("input.txt");
C) Scanner inputFile = new Scanner(new File(input.txt);
D) Scanner inputFile = new Scanner(new InputFile(input.txt);
E) Scanner inputFile = new Scanner(new File("input.txt");

Question 8

A logical expression can be described by a ________________ that lists all possible combinations of values for the variables involved in an expression.

A) palindrome
B) nested loop
C) equality operator
D) switch statement
E) truth table

Question 9

Every if statement requires an associated else statement, but not every else statement requires an associated if statement.

Question 10

Which of the following logical operators has the highest precedence?

A) !
B) &&
C) ||
D) <
E) >

Question 11

In Java, a boolean expression is limited to having exactly 2 logical operators.

Question 12

A while statement always executes its loop body at least once.

Question 13

What happens if a case in a switch statement does not end with a break statement?

A) The program will not compile.
B) The switch statement will never execute.
C) It will cause an infinite loop.
D) The switch statement will execute the next case statement as well.
E) The case will never be executed.

Question 14

Suppose we want to condition an if statement on whether two String objects, referenced by stringOne and stringTwo, are the same. Which of the following is the correct way to achieve this?

A) if(stringOne == stringTwo)
B) if(stringOne.compareTo(stringTwo))
C) if(stringOne.equals(stringTwo))
D) if(stringOne != stringTwo)
E) if(stringOne === stringTwo)

Question 15

Which of the following statements best describes the flow of control in the main method of a Java program that has no conditionals or loops?

A) Program statements are all executed at the same time.
B) Program statements are executed according to their priority, which is specified by the programmer.
C) Program statements are executed linearly, with earlier statements being executed first.
D) Program statements are executed linearly, with later statements being executed first.
E) Some program statements are executed at the same time, and others are executed in a linear manner.

Question 16

Which of the following is not a valid relational operator in Java

A) <=
B) >
C) ==
D) <>
E) !=

Question 17

Which of the following best describes this code snippet? if (count != 400)
System.out.println("Hello World!");

A) If the variable count is exactly equal to 400, "Hello World" will be printed.
B) If the variable count is not equal to 400, "Hello World" will be printed.
C) If the variable count is close to, but not greater than, 400, "Hello World" will be printed.
D) If the variable count is exactly equal to 399 or 401, "Hello World" will be printed.
E) This code will not compile.

Question 18

The ___________________ statement causes current iteration of a loop to stop and the condition to be evaluated again, either stopping the loop or causing the next iteration.

A) stop
B) halt
C) continue
D) break
E) switch

Question 19

The following snippet of code will not compile because the second part of the if statement needs to be on the second line.
if(a <
b) System.out.println("a is less than b");

Question 20

A _______________ loop always executes its loop body at least once.

A) while
B) for
C) do
D) repeat
E) There are no loop structures with this property in Java.

Question 21

What is wrong with the following snippet of code? Rewrite it so it produces the correct output.
if(a <
b)
if(a ==
c)
System.out.println("a < b and a == c");
else
System.out.println("a is not less than b");

Question 22

Write a code fragment that determines how many times the character 'A' appears in a String object called name.

Question 23

An infinite loop is a compile-time error.

Question 24

Write a code fragment that allows a user to continue inputting numbers until she enters a sentinel value of 0. Then print the sum of all the numbers she entered. You may assume that a Scanner object called input has already been created.

Question 25

A Scanner object can use delimiters other than a space.

Question 26

Rewrite the following code fragment using a for loop instead of a while loop.
int i = 0;
while(i < 50) {
System.out.println(i);
i+=2;
}

Question 27

The following code compiled, but while running it the program appears to hang (e.g. nothing happens). This is a clear sign of an infinite loop. What part of this code fragment caused the infinite loop?
while(i < 50); {
System.out.println(i);
i+=2;
}

Question 28

It is possible to implement a switch statement using if statements.

Question 29

Write a switch statement that switches on an integer variable named val. If val is 2 or 15, then output "Hello World." For all other values, output "Goodbye World."

Question 30

Write a short code fragment that uses a while loop to verify that the user enters a positive integer as input. You may assume that a Scanner object called input has already been created.

Question 31

Rewrite the following for loop as a while loop.
for(int i = 0; i < MAX; i++)
//loop body

Question 32

What is output by the following code fragment?
int num = 0;
int max = 10;
while(num < max) {
System.out.println(num);
num += 2;
}

Question 33

Write a for loop to print the even numbers from 1 to 100 (inclusive).

Question 34

The relational operators should not be used to test the equality of objects.

Question 35

Write a snippet of code that determines which of two integer variables, intOne and intTwo, contains a larger number, and print out the larger one. If they are equal, the output should say that.

Question 36

The Scanner object can be used to read text files.

Question 37

Assume numOne and numTwo are integers. How many times might the following code print out grape? Explain your answer.
if(numOne > numTwo && numOne < numTwo)
System.out.println("grape");
else {
if(numOne == numTwo) {
System.out.println("grape");
if(numOne > numTwo)
System.out.println("grape");
}//end if numOne == numTwo
}//end else

Question 38

Write a short application that takes in a String from the user and prints it out backwards.

Question 39

Write a do loop that verifies that the user enters an odd value. You may assume that a Scanner object called input has already been created.

Question 40

Using a while loop, write a code fragment that computes the sum of the first n natural numbers (i.e. 1, 2, 3, 4, ... n), where n is an integer variable already defined in the program.