Looping & Random Numbers

Question 1

A structure that allows repeated execution of a block of statements.

Answer 1

Loop

Question 2

What must be evaluated before the loop body executes?

Answer 2

A Boolean Expression

Question 3

In order for the loop body to execute, a Boolean expression must be evaluated to be what?

Answer 3

The Boolean expression must be true.

Question 4

A block of statements. It can be a single statement, or a block of statements between curly braces.

Answer 4

Loop Body

Question 5

What are the two categories of loops?

Answer 5

1. Conditional Loop
2. Count-controlled Loop

Question 6

This category of loops executes as long as a particular condition exists.

Answer 6

Conditional Loop

Question 7

This category of loops repeats a specific number of times.

Answer 7

Count-controlled Loop

Question 8

What are the three elements of a count-controlled loop?

Answer 8

1. Initialization - Initialize a control variable to a starting value.
2. Increment/Decrement - Update the control variable during each iteration.
3. Condition - Test the control variable by comparing it to a maximum value. When the control variable reaches its maximum value, the loop terminates.

Question 9

What is the ++ operator called?

Answer 9

Increment

Question 10

What is the – called?

Answer 10

Decrement

Question 11

What do the increment and decrement operators do?

Answer 11

They add and subtract one from their operands.

Question 12

What does it mean to increment a value?

Answer 12

To increase the value by one.

Question 13

What does it mean to decrement a value?

Answer 13

To decrease the value by one.

Question 14

x = 6;
System.out.print(x++);

What would the output be? What would the new value of x be?

Answer 14

Output: 6
New Value of x: 7

Question 15

x = 6;
System.out.print(++x);

What would the output be? What would the new value of x be?

Answer 15

Output: 7
New value of x: 7

Question 16

Used to iterate a part of the program repeatedly until the specified Boolean condition is true. As soon as the Boolean condition becomes false, the loop automatically stops.

Answer 16

While Loop

Question 17

This loop is also considered as a repeating if statement.

Answer 17

While Loop

Question 18

What are the two important parts of a while loop?

Answer 18

1. A boolean expression that is tested for a true or false value
2. A statement or block of statements that is repeated as long as the expression is true.

Question 19

This loop is known as a pretest loop, which means it tests its expression before each iteration.

Answer 19

While Loop

Question 20

What would the output be?

int number = 6;
while (number <= 5) {
System.out.println(“Hello”);
number++;
}

Answer 20

This program would have no output since the condition is false.

Question 21

This loop does not have a way of stopping, it continues to repeat until the program is interrupted.

Answer 21

Infinite Loops

Question 22

int number = 1;
while (number <= 5){
System.out.println(“Hello”);
}

What will happen to the loop in this program?

Answer 22

The loop in this program will repeat infinitely and will not be terminated since the condition is always true since the value of the number is always 1

Question 23

What will happen if you put a semicolon after the first condition?

int number = 1;
while (number <= 5);{
System.out.println(“Hello”)
x++
}

Answer 23

An infinite loop will be created.

Question 24

This loop is a posttest loop, which means its Boolean expression is tested after each iteration.

Answer 24

Do-while Loop

Question 25

This loop looks something like an inverted while loop.

Answer 25

Do-while Loop

Question 26

What does the do-while loop look like?

Answer 26

An inverted while loop

Question 27

What is the syntax for do-while loops?

Answer 27

do {
Statement/s;
} while (BooleanExpression);

Question 28

What is the syntax for while loops?

Answer 28

while (BooleanExpression) {
Statement/s;
}

Question 29

“The do-while loop must be terminated with a semicolon.”

Is the statement above TRUE or FALSE?

Answer 29

TRUE

Question 30

What is the difference between the while loop and do-while loop?

Answer 30

The do-while loop always performs at least one iteration, even if the boolean expression is false to begin with.

Question 31

int num= 6;
while(num<=5) {
System.out.println(“Hello World”);
num++;
}

Will the loop be executed?

Answer 31

Loop will not be executed since the condition is False.

Question 32

Explain what happens below.

num= 6;
do {
System.out.println(“Hello World”);
num++;
}while(num<=5);

Answer 32

The loop will print Hello world at least once, then the loop will terminate because the condition is false.

Question 33

What are some examples of uses for random numbers in programming tasks?

Answer 33

• Commonly used in games
• Useful in simulation programs
• Useful in statistical programs that must randomly select data for analysis
• Commonly used in computer security to encrypt sensitive data

Question 34

What is the syntax for importing the Random class?

Answer 34

import java.util.Random;

Question 35

What is the syntax for creating an object from the random class?

Answer 35

Random randomNumbers = new Random();

Where randomNumbers is the name of the object.

Question 36

This Random class method returns the next random number as a double. The number will be within the range of 0.0 through 1.0.

Answer 36

nextDouble()

Question 37

This Random class method returns the next random number as a float. The number will be within the range of 0.0 through 1.0

Answer 37

nextFloat()

Question 38

This Random class method returns the next random number as an int. The number will be within the range of an int, which is −2,147,483,648 to +2,147,483,648

Answer 38

nextInt()

Question 39

This Random class method accepts an integer argument, n. It returns a random number as an int. The number will be within the range of 0 through n.

Answer 39

nextInt(int n)

Question 40

This loop is the most used one out of the three loops

Answer 40

For Loop

Question 41

This loop is ideal for performing a known number of iterations

Answer 41

For Loop

Question 42

In this loop, the three elements of the loop can be found in one line.

Answer 42

For Loop

Question 43

What is the syntax for for loops?

Answer 43

for (initialization; condition; increment/decrement) {
Statement/s;
}

Question 44

What are the steps of executing a for loop?

Answer 44

Step 1. Perform the initialization expression
Step 2. Evaluate the test expression. If it is true, go to Step 3. Otherwise, terminate the loop.
Step 3. Execute the body of the loop.
Step 4. Perform the update expression, then go back to step 2.

Question 45

What happens if you put a semicolon at the end of the for clause before the loop body?

Answer 45

The semicolon signifies the end of the loop prematurely.

Question 46

What would the output be?

int x;
for (x=1; x<=5; x++) {
System.out.print(x + “ “);
}

Answer 46

Output: 1 2 3 4 5

Question 47

What would the output be?

int x;
for (x=1; x<=5; x++); {
System.out.print(x + “ “);
}

Answer 47

Output: 6

The loop is terminated prematurely because of the semicolon at the end of the for clause.

Question 48

A sum of numbers that accumulates with each iteration of a loop.

Answer 48

Running Total

Question 49

This is the variable used to keep the running total.

Answer 49

Accumulator

Question 50

What type of loop is shown below?

int num, count=0;
for(num=10; num<=15; num++){
if (num % 2== 0)
count++;
}

Answer 50

For loop

Question 51

What type of loop is shown below?

int x= 1;
Scanner input = new Scanner(System.in);
while(x<=5) {
System.out.print(“Input a number “ + x + “ “);
num = input.nextInt();
x++;
}

Answer 51

While loop

Question 52

What type of loop is shown below?

int num, x=1;
char ch;
Scanner input = new Scanner(System.in);
do {
System.out.print(“Input a number “);
num = input.nextInt();
System.out.print(“Input again? “);
ch = input.next().charAt(0);
} while(ch==’y’ || ch==’Y’);

Answer 52

Do-while Loop