Java Arrays & Collections – Storing Data Like a Pro!

Hello Hello guys..I'm Dulanka Nimsara and today is our 5th day ! Ok, Lets's Start! Data is the heart of any program! But how do we store, organize, and manage data efficiently? That’s where Arrays and Collections come in! Today, we’ll explore these powerful tools that help Java handle data like a pro.

What Are Arrays?

Imagine a row of lockers – each locker has a number and can store one item. That’s exactly how an array works!

? An array is a fixed-size collection of similar data types stored in a single variable.

Why Use Arrays?

? Stores multiple values under one name

? Faster access using index numbers

? Organized data management

How Arrays Work

Each element in an array has an index number, starting from 0.

Limitations of Arrays

?? Arrays are fixed in size – once you define an array, you cannot change its length.

What if we need a flexible data structure? Enter Collections!

What Are Collections?

Collections are dynamic data structures that grow and shrink as needed. Think of them as smart containers that can store, sort, and manage data more efficiently.

Why Use Collections?

? No fixed size – Can grow or shrink as needed

? Pre-built methods – Sorting, searching, and more!

? More powerful than arrays

Common Collection Types in Java

List (Ordered Collection – Like an Expandable Array)

A List stores elements in order and allows duplicates.

• Examples : ArrayList, LinkedList
• Use Case : Storing a list of student names where order matters.

Set (Unique Elements – No Duplicates Allowed)

A Set stores only unique values and has no specific order.

• Examples : HashSet, TreeSet
• Use Case : Keeping a collection of unique usernames

Map (Key-Value Pairs – Like a Dictionary)

A Map stores data as key-value pairs – like a dictionary!

• Examples : HashMap, TreeMap
• Use Case : Storing student IDs with their names (ID → Name)

Arrays vs. Collections – When to Use What?

• Use Arrays when you need simple, fixed-size storage
• Use Collections when you need dynamic, flexible data structures

Key Takeaways!

? Arrays are great for fixed-size storage

? Collections are flexible, dynamic, and more powerful

? Lists, Sets, and Maps help manage data efficiently in Java

Next up : Day 6 – Exception Handling: Writing Error-Proof Code!