Java - Collections - Hands-on

Learning Objectives

• Understand how to use List, Set, and Map in Java.
• Implement real-world scenarios using Java Collections.
• Practice retrieving, updating, and manipulating collections.

---

Exercise 1: Managing a Library (Using List)

Problem Statement

A library needs a system to store a list of available books. Implement a List to store book titles and perform the following operations:

1. Add books to the library.
2. Display all books.
3. Remove a specific book.
4. Search for a book by title.

Input & Output

Input:

• A list of book titles.
• A title to remove.
• A title to search.

Expected Output:

• The list of books after addition.
• The list of books after removal.
• A message indicating whether a book is found or not.

---

Exercise 2: Unique Student Roll Numbers (Using Set)

Problem Statement

A university stores student roll numbers and wants to ensure that duplicate entries are not added. Implement a Set to store roll numbers and perform the following:

1. Add new roll numbers.
2. Display all roll numbers.
3. Attempt to add a duplicate roll number and observe the output.

Input & Output

Input:

• A set of student roll numbers.
• A roll number to add.

Expected Output:

• The set of roll numbers after adding elements.
• No duplicate roll numbers should be present.

---

Exercise 3: Phonebook Directory (Using Map)

Problem Statement

A phonebook application stores contacts with names and phone numbers. Implement a Map to store contact details and perform the following:

1. Add contacts to the phonebook.
2. Retrieve a contact’s phone number using the name.
3. Display all contacts.

Input & Output

Input:

• A set of name-phone number pairs.
• A name to search.

Expected Output:

• The list of contacts after addition.
• The phone number associated with a given name.

---

Java Collections - Sorting Exercises

Exercise 4: Sorting Books by Title (Using Comparable)

Problem

A library needs to sort books by title in alphabetical order. Implement the Comparable interface to allow sorting of book objects.

1. Define a Book class with title and author.
2. Implement the Comparable interface to sort books by title.
3. Add books to a List and sort them.
4. Display the sorted list.

Input & Output

Input:

• A list of books with title and author.

Expected Output:

• The list of books sorted by title.

---

Exercise 5: Sorting Students by Age (Using Comparator)

Problem

A university maintains student records and needs to sort them by age. Implement the Comparator interface for custom sorting.

1. Define a Student class with name and age.
2. Create a Comparator implementation to sort students by age.
3. Add students to a List and sort them.
4. Display the sorted list.

Input & Output

Input:

• A list of students with name and age.

Expected Output:

• The list of students sorted by age in ascending order.

---

Exercise 6: Sorting Products by Price (Using Comparator with Lambda)

Problem

An e-commerce store needs to sort products by price. Use Java 8 lambdas to define the sorting logic.

1. Define a Product class with name and price.
2. Use a lambda expression to sort products by price.
3. Add products to a List and sort them.
4. Display the sorted list.

Input & Output

Input:

• A list of products with name and price.

Expected Output:

• The list of products sorted by price in ascending order.

---

← Excercise 11

Next Topic TBD →

---

🔗 Related Topics:

• Collections
• ArrayList
• Sorting Collections

• Streams API