Loops

Question 1

What are the 4 kinds of loops we’ve learned?

Answer 1

while, do-while, for and for-each loops

Question 2

What is the loop body?

Answer 2

The loop body is the statements inside the loop that are executed every iteration

Question 3

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

Answer 3

A while loop checks the loop-continuation-condition before entering the loop body, while a do-while loop checks it after the first iteration

Question 4

When are while and do-while loops generally used?

Answer 4

When the number of iterations is not predetermined

Question 5

When is a for loop generally used?

Answer 5

When the loop body needs to be executed a certain number of times

Question 6

What is the syntax of the do-while loop?

Answer 6

do {
body of the loop;
} while (testExpression)

Question 7

What is the syntax of the for loop?

Answer 7

for (initialExpression; testExpression; updateExpression) {
//body of the loop;
}

Question 8

What is i after the following for loop?

int y = 0;
for (int i = 0; i<10; ++i) {
y += i;
}

A. 9
B. 10
C. 11
D. undefined

Answer 8

D. undefined
Explanation: The scope of i is inside the loop. After the loop, i is not defined.

Question 9

how would you loop through and print the numbers in this array?

int[] groupNumbers = {11, 27, 65, 82, 55};

Answer 9

for (int i = 0; i < groupNumbers.length; i++){
System.out.println(groupNumbers[i]);}
Or
For(num : groupNumbers) {
System.out.println(num);}

Question 10

what will be the output of this for loop?
int number = 1;
for(int i = 1; i < =4; i++){
number *= i;
System.out.println(number);

Answer 10

1
2
6
24

Question 11

when finding/comparing the length of an array for a for loop why do we use:
A. i < arrrayName.length
vs
B. 1 <= arrrayName.length

Answer 11

because indexing an array starts at the number 0, and so the last element in the array is actually located at the length - 1.

Question 12

What is an iteration?

Answer 12

One time through the body of a loop.

Question 13

A while loop runs until…….

Answer 13

A while loop runs until the test condition is made false.

Question 14

What is the syntax for a while loop?

Answer 14

while (testExpression) {
//loop body
}

Question 15

How does a while loop work?

Answer 15

1) It evaluates the boolean test expression:
a) If the value is false, the entire loop is skipped.
b) If the value is true, the the body of the loop is executed
and the loops starts over.

Question 16

What will the difference in the output of these 2 different types of loops?
1) int i = 1;
while(i <= 3) {
System.out.println(i);
i++;
}
2) for(int i = 1; i <= 3; i++) {
System.out.println(i);
}

Answer 16

Nothing. The output for both is:
1
2
3

Question 17

When would we use a while loop instead of a for loop?

Answer 17

When the necessary number of iterations of the loop isn’t known.

Question 18

When does an infinite loop occur and what is a the usual result?

Answer 18

An infinite loop occurs when the test expression always evaluates as true. When this happens the loop repeats infinitely and the program will eventually terminate abnormally.

Question 19

What is another name for a for-each loop?

Answer 19

A for-each loop is also called an enhanced-for loop.

Question 20

Why would we use a for-each loop instead of a normal loop?

Answer 20

A for-each loop is easier to write and read/understand. Note: We also should also want to access every element of an array or ArrayList.

Question 21

What is the syntax for using a for-each loop to loop through the elements in the ArrayList flavor and print out the elements we call tastes?

Answer 21

for(String tastes : flavor) {
System.out.println(tastes);

Question 22

How do we specify the beginning, ending or increment of a for-each loop?

Answer 22

We don’t. For-each will automatically loop through the whole list.

Question 23

What would make you use a regular loop instead of a for-each loop?

Answer 23

We don’t want to access all the elements of the array/ArrayList.
We need the index values of the elements of the array/ArrayList.