Topic 9.4: Working with Selected classes from the Java API - Declare and use an ArrayList of a given type

Question 1

Write a code snippet using the indexOf() method to find the index of a specific element in an ArrayList.

Answer 1

ArrayList<String> names = new ArrayList<>();
names.add("Alice");
names.add("Bob");</String>

int index = names.indexOf(“Bob”);

Question 2

This method returns true if the ArrayList has no elements, indicating that it is empty. Otherwise, it returns false.

Answer 2

What does the isEmpty() method return in an ArrayList?

Question 3

What does the clear() method do in an ArrayList?

Answer 3

This method removes all elements from an ArrayList, resulting in an empty ArrayList.

Question 4

What is the purpose of the clear() method in an ArrayList?

Answer 4

This method is used to remove all elements from an ArrayList, resulting in an empty ArrayList. It does not delete the ArrayList object itself but only removes its contents.

Question 5

This method returns true if the specified element is found in the ArrayList, and false otherwise.

Answer 5

What does the contains() method return in an ArrayList?

Question 6

This method is used to check whether an ArrayList contains a specific element. It returns a boolean value indicating whether the element is present in the ArrayList or not.

Answer 6

What is the purpose of the contains() method in an ArrayList?

Question 7

Provide a code snippet that demonstrates how to replace an element in an ArrayList.

Answer 7

ArrayList<String> fruits = new ArrayList<>();
fruits.add("Apple");
fruits.add("Orange");
fruits.add("Banana");

fruits.set(1, "Mango");

Question 8

How can you retrieve an element from an ArrayList?

Answer 8

To accomplish this , you can use the get(index) method.

ElementType element = list.get(index);

Question 9

To accomplish this you can use the add() method.

ArrayList<ElementType> list = new ArrayList<>();
list.add(element);

Answer 9

How do you append elements to the end of an ArrayList?

Question 10

To accomplish this , you can use the get(index) method.

ElementType element = list.get(index);

Answer 10

How can you retrieve an element from an ArrayList?

Question 11

How can you insert elements at specific positions within an ArrayList?

Answer 11

To accomplish this, you can use the add(index, element) method

list.add(index, element);

Question 12

What does the isEmpty() method return in an ArrayList?

Answer 12

This method returns true if the ArrayList has no elements, indicating that it is empty. Otherwise, it returns false.

Question 13

You can accomplish this using the indexOf() method.

It returns the index of the first occurrence of the element if found, or -1 if the element is not present in the ArrayList.

Answer 13

How can you find the index of a specific element in an ArrayList

Question 14

You can check this using the isEmpty() method.

It returns a boolean value indicating whether the ArrayList has any elements or not.

Answer 14

How can you check if an ArrayList is empty using the isEmpty() method?

Question 15

What does the contains() method return in an ArrayList?

Answer 15

This method returns true if the specified element is found in the ArrayList, and false otherwise.

Question 16

How can you remove elements from an ArrayList based on their object reference?

Answer 16

To accomplish this you can use the remove(element) method.

list.remove(element);

Question 17

Write a code snippet using the clear() method to remove all elements from an ArrayList.

Answer 17

ArrayList<String> names = new ArrayList<>();
names.add("Alice");
names.add("Bob");

names.clear();

Question 18

Write a code snippet using the contains() method to check if an ArrayList contains a specific element.

Answer 18

ArrayList<Integer> numbers = new ArrayList<>();
numbers.add(5);
numbers.add(10);

boolean contains = numbers.contains(10);

Question 19

To accomplish this, you can use the add(index, element) method

list.add(index, element);

Answer 19

How can you insert elements at specific positions within an ArrayList?

Question 20

to accomplish this you can use the remove(index) method.

list.remove(index);

Answer 20

How can you remove elements from an ArrayList based on their index?

Question 21

How can you determine the number of elements in an ArrayList?

Answer 21

To achieve this, you can use the size() method.

int size = list.size();

Question 22

Write a code snippet using the isEmpty() method to check if an ArrayList is empty.

Answer 22

ArrayList<String> names = new ArrayList<>();
names.add("Alice");

boolean isEmpty = names.isEmpty();

Question 23

Provide a code snippet that demonstrates how to remove an element from an ArrayList based on its object reference.

Answer 23

ArrayList<Integer> numbers = new ArrayList<>();
numbers.add(5);
numbers.add(10);
numbers.add(15);

numbers.remove(Integer.valueOf(10));

Question 24

How can you find the index of a specific element in an ArrayList

Answer 24

You can accomplish this using the indexOf() method.

It returns the index of the first occurrence of the element if found, or -1 if the element is not present in the ArrayList.

Question 25

This method returns the index of the first occurrence of the specified element in the ArrayList. If the element is not found, it returns -1.

Answer 25

What does the indexOf() method return in an ArrayList?

Question 26

Provide a code snippet that demonstrates how to determine the size of an ArrayList.

Answer 26

ArrayList<String> fruits = new ArrayList<>();
fruits.add("Apple");
fruits.add("Orange");
fruits.add("Banana");

int size = fruits.size();
System.out.println(size);

Question 27

Provide a code snippet that demonstrates how to insert an element at a specific position within an ArrayList.

Answer 27

ArrayList<String> colors = new ArrayList<>();
colors.add("Red");
colors.add("Blue");
colors.add(1, "Green");

Question 28

Provide a code snippet that demonstrates how to append an element to the end of an ArrayList.

Answer 28

ArrayList<String> fruits = new ArrayList<>();
fruits.add("Apple");

Question 29

What is the purpose of the ArrayList class in Java?

Answer 29

The purpose of the ArrayList class in Java is to provide a resizable and dynamic array implementation that serves as a container for storing a collection of objects.

It allows for flexible management of elements, allowing the ArrayList to grow or shrink in size as elements are added or removed.

Question 30

How can you replace an element in an ArrayList?

Answer 30

To modify an element in an ArrayList, you can use the set(index, element) method. This method replaces the element at the specified index with the specified element, updating the ArrayList with the new value while preserving its structure.

list.set(index, element);

Question 31

How do you append elements to the end of an ArrayList?

Answer 31

To accomplish this you can use the add() method.

ArrayList<ElementType> list = new ArrayList<>();
list.add(element);

Question 32

How can you remove elements from an ArrayList based on their index?

Answer 32

to accomplish this you can use the remove(index) method.

list.remove(index);

Question 33

Provide a code snippet that demonstrates how to remove an element from an ArrayList based on its index.

Answer 33

ArrayList<String> fruits = new ArrayList<>();
fruits.add("Apple");
fruits.add("Orange");
fruits.add("Banana");

fruits.remove(1);

Question 34

ArrayList<String> fruits = new ArrayList<>();
fruits.add("Apple");
fruits.add("Orange");
fruits.add("Banana");

fruits.remove(1);

Answer 34

Provide a code snippet that demonstrates how to remove an element from an ArrayList based on its index.

Question 35

This method removes all elements from an ArrayList, resulting in an empty ArrayList.

Answer 35

What does the clear() method do in an ArrayList?

Question 36

To achieve this, you can use the size() method.

int size = list.size();

Answer 36

How can you determine the number of elements in an ArrayList?

Question 37

ArrayList<String> fruits = new ArrayList<>();
fruits.add("Apple");
fruits.add("Orange");
fruits.add("Banana");

int size = fruits.size();
System.out.println(size);

Answer 37

Provide a code snippet that demonstrates how to determine the size of an ArrayList.

Question 38

To accomplish this you can use the remove(element) method.

list.remove(element);

Answer 38

How can you remove elements from an ArrayList based on their object reference?

Question 39

What does the indexOf() method return in an ArrayList?

Answer 39

This method returns the index of the first occurrence of the specified element in the ArrayList. If the element is not found, it returns -1.

Question 40

How can you remove elements from an ArrayList, and what are the methods involved?

Answer 40

You can remove elements from an ArrayList using two methods: remove(index) and remove(element).

Question 41

How can you check if an ArrayList is empty using the isEmpty() method?

Answer 41

You can check this using the isEmpty() method.

It returns a boolean value indicating whether the ArrayList has any elements or not.

Question 42

What is the purpose of using an ArrayList over a regular array when dealing with the issue of running out of room?

Answer 42

The purpose of using an ArrayList over a regular array is to overcome the problem of running out of room. With an ArrayList, you don’t need to manually create a larger array and copy the contents. The ArrayList handles this internally, providing benefits such as not having to write code for resizing and ensuring that all references to the ArrayList remain valid.

Question 43

What is the purpose of the contains() method in an ArrayList?

Answer 43

This method is used to check whether an ArrayList contains a specific element. It returns a boolean value indicating whether the element is present in the ArrayList or not.

Question 44

ArrayList<Integer> numbers = new ArrayList<>();
numbers.add(5);
numbers.add(10);
numbers.add(15);

numbers.remove(Integer.valueOf(10));

Answer 44

Provide a code snippet that demonstrates how to remove an element from an ArrayList based on its object reference.