Stacks

Question 1

In a stack data structure, what is the primary characteristic of how items are accessed?
a) First-in, first-out (FIFO)
b) Last-in, first-out (LIFO)
c) Random access
d) First-in, last-out (FILO)

Answer 1

b) Last-in, first-out (LIFO)

Question 2

What operation is used to add an item to the top of the stack?
a) Insert
b) Pop
c) Push
d) Append

Answer 2

c) Push

Question 3

When an item is removed from a stack, what operation is being performed?
a) Push
b) Pop
c) Peek
d) Delete

Answer 3

b) Pop

Question 4

What does the peek operation do in a stack?
a) Removes the top item from the stack
b) Adds an item to the stack
c) Views the top item without removing it
d) Clears all items from the stack

Answer 4

c) Views the top item without removing it

Question 5

In the Item class, what is the purpose of the getter and setter for the name property?
a) To increase security
b) To allow controlled access and modification of the name
c) To store multiple data types
d) To define static variables

Answer 5

b) To allow controlled access and modification of the name

Question 6

What is the maximum size of the Stack initially set to if no parameter is passed?
a) 5
b) 10
c) 15
d) 20

Answer 6

b) 10

Question 7

Which method resizes the items array if the stack exceeds the maximum count?
a) resizeItemsArray()
b) resizeStack()
c) expandArray()
d) extendStack()

Answer 7

a) resizeItemsArray()

Question 8

In Java, why is it necessary to create a new array and copy items when resizing?
a) Arrays in Java are immutable
b) Java does not allow array resizing
c) Collection classes are not available
d) Arrays have fixed data types

Answer 8

b) Java does not allow array resizing

Question 9

How many additional slots are added to the stack’s item array during a resize operation?
a) 3
b) 5
c) 7
d) 10

Answer 9

b) 5

Question 10

What happens to the stackCount variable when an item is pushed onto the stack?
a) It is decremented
b) It remains unchanged
c) It is incremented
d) It is reset to zero

Answer 10

c) It is incremented

Question 11

In the Stack class, which method returns the current number of items in the stack?
a) getMaxCount()
b) getStackCount()
c) stackCount()
d) countItems()

Answer 11

b) getStackCount()

Question 12

What is the purpose of overriding the toString() method in the Stack class?
a) To change the stack’s data structure
b) To modify how the stack is displayed when printed
c) To reset the stack
d) To perform operations on stack elements

Answer 12

b) To modify how the stack is displayed when printed

Question 13

Why does the Stack class not provide a setter for stackCount?
a) It does not store any values
b) stackCount should only be changed internally by the Stack class
c) stackCount is public and can be accessed directly
d) stackCount is a constant

Answer 13

b) stackCount should only be changed internally by the Stack class

Question 14

In a stack, what happens when stackCount exceeds maxCount during a push operation?
a) The stack is reset
b) A new item cannot be added
c) resizeItemsArray() is called
d) Items are shifted downward

Answer 14

c) resizeItemsArray() is called

Question 15

What does the toString() method in the Stack class display?
a) Only the top item
b) All items in reverse order with indices
c) The size of the stack
d) Only the first item

Answer 15

b) All items in reverse order with indices

Question 16

What will happen if we call the pop() method on an empty stack?
a) It will return null
b) It will throw an exception
c) It will return a default item
d) It will add a new item

Answer 16

b) It will throw an exception

Question 17

What is the purpose of the stack used by the Java Virtual Machine (JVM) during program execution?
a) To manage variable types
b) To control execution order of methods
c) To store user inputs
d) To optimize memory usage

Answer 17

b) To control execution order of methods

Question 18

In the DataStructuresExamples class, what type of object is stack?
a) ArrayList
b) Queue
c) Stack
d) HashMap

Answer 18

c) Stack

Question 19

Which item would be at the top of the stack after the following operations? stack.push(firstMan); stack.push(apollo13); stack.push(rogueOne);
a) firstMan
b) rogueOne
c) apollo13
d) The stack is empty

Answer 19

b) rogueOne

Question 20

If you wanted to access the bottom item in the stack, what operation would you perform?
a) Pop all items until the last one remains
b) Use peek()
c) Set stackCount to zero
d) Access the array directly

Answer 20

a) Pop all items until the last one remains