unit 3-4

Question 1

What is a boolean expression?

Answer 1

An expression that evaluates to true or false.

Question 2

What are the boolean literals in Java?

Answer 2

true and false

Question 3

What operator is used for equality comparison?

Answer 3

==

Question 4

What does != mean?

Answer 4

Not equal to

Question 5

What does > mean in Java?

Answer 5

Greater than

Question 6

What does >= mean?

Answer 6

Greater than or equal to

Question 7

What does < mean in Java?

Answer 7

Less than

Question 8

What does <= mean?

Answer 8

Less than or equal to

Question 9

What operator is used for logical AND?

Answer 9

&&

Question 10

What operator is used for logical OR?

Answer 10

||

Question 11

What operator is used for logical NOT?

Answer 11

!

Question 12

What is the result of true && false?

Answer 12

false

Question 13

What is the result of true || false?

Answer 13

true

Question 14

What is the result of !false?

Answer 14

true

Question 15

What is the correct way to write an if statement in Java?

Answer 15

if (condition) {
// code
}

Question 16

How do you write an if-else statement?

Answer 16

if (condition) {
// true block
} else {
// false block
}

Question 17

What is an else if?

Answer 17

An additional condition checked only if previous ones are false.

Question 18

When is an else block executed?

Answer 18

Only when all previous if/else if conditions are false.

Question 19

What does this return? “hello”.equals(“Hello”)

Answer 19

false — case-sensitive comparison.

Question 20

What method is used to compare strings for equality?

Answer 20

.equals()

Question 21

Can you use == to compare strings reliably?

Answer 21

No. It compares memory addresses, not content.

Question 22

What is a nested if?

Answer 22

An if inside another if.

Question 23

What is short-circuit evaluation?

Answer 23

Java stops evaluating a boolean expression as soon as the result is known.

Question 24

What is DeMorgan’s Law?

Answer 24

Rules for distributing ! across && and ||:
!(A && B) → !A || !B
!(A || B) → !A && !B

Question 25

What is the output of this code? int x = 5; if (x > 3 && x < 10) { System.out.print("Yes"); }

Answer 25

Yes

Question 26

What is a loop?

Answer 26

A control structure that repeats code.

Question 27

What are the 3 loop types in Java?

Answer 27

while, for, and enhanced for loops.

Question 28

What does a while loop do?

Answer 28

Repeats as long as the condition is true.

Question 29

Give a simple while loop example.

Answer 29

int i = 0; while (i < 5) { System.out.print(i); i++; }

Question 30

What must you avoid in a while loop?

Answer 30

Infinite loops — make sure the condition becomes false eventually.

Question 31

What is the format of a for loop?

Answer 31

for (int i = 0; i < 5; i++) { // code }

Question 32

When should you use a for loop over while?

Answer 32

When the number of iterations is known.

Question 33

What is an enhanced for loop?

Answer 33

A loop used to iterate over arrays or collections. Example: for (int x : arr) { System.out.println(x); }

Question 34

Can you modify an array with an enhanced for loop?

Answer 34

Not directly — use index-based loop to modify.

Question 35

How do you exit a loop early?

Answer 35

Use break;

Question 36

How do you skip to the next iteration of a loop?

Answer 36

Use continue;

Question 37

What is nested iteration?

Answer 37

A loop inside another loop.

Question 38

How many times does this print? for (int i = 0; i < 2; i++) { for (int j = 0; j < 3; j++) { System.out.print("*"); } }

Answer 38

6 times (2 * 3)

Question 39

What is loop tracing?

Answer 39

Following variable values step by step during loop execution.

Question 40

What is the output of: for (int i = 5; i > 0; i--) { System.out.print(i); }

Answer 40

54321

Question 41

What type of loop is this? while (true) { // endless }

Answer 41

Infinite loop

Question 42

Why avoid modifying a list during iteration?

Answer 42

It may cause errors or skip elements.

Question 43

Can a for loop condition use &&?

Answer 43

Yes. Example: for (int i = 0; i < 10 && arr[i] != 0; i++) {}

Question 44

What loop is best for traversing an array?

Answer 44

Use for or enhanced for.

Question 45

How do you count specific items in a loop?

Answer 45

Use an if inside the loop and a counter variable.

Question 46

What happens if you forget to update the loop variable?

Answer 46

Infinite loop.

Question 47

How can loops help with String processing?

Answer 47

You can use .charAt(i) in a loop to check each character.

Question 48

What’s a common use of nested loops?

Answer 48

Working with 2D arrays.

Question 49

When does this loop stop? int x = 10; while (x > 0) { x--; }

Answer 49

After 10 iterations.

Question 50

How would you reverse a string using a loop?

Answer 50

Loop from last index to 0, printing each character.