ArrayList and LinkedList in Java

📋 ArrayList and LinkedList in Java

In the Java Collections Framework, both ArrayList and LinkedList in Java provide dynamic list implementations. They allow you to store and manipulate ordered collections of elements.

Although they share the List interface, their internal workings and performance differ, making it important to know when to use each.

⚙️ What is ArrayList?

An ArrayList is backed by a resizable array. It stores elements in contiguous memory locations, allowing fast random access using indices.

However, resizing the array or inserting/removing elements in the middle can be costly due to shifting elements.

import java.util.ArrayList;

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

// Access element by index
String first = fruits.get(0); // "Apple"

🔗 What is LinkedList?

A LinkedList is implemented as a doubly linked list. Each element (node) holds data and references to the previous and next nodes.

This structure allows efficient insertions and deletions anywhere in the list but slower random access compared to ArrayList.

import java.util.LinkedList;

LinkedList fruits = new LinkedList<>();
fruits.add("Apple");
fruits.add("Banana");
fruits.add("Cherry");

// Accessing element requires traversal
String first = fruits.get(0); // "Apple"

💡 When to Use Which?

• Use ArrayList when you need fast random access and your application performs many read operations.
• Use LinkedList if your application frequently adds or removes elements from the beginning or middle of the list.
• For most general cases, ArrayList is preferred due to better cache performance.

🛠️ Common Methods in Both

Both classes implement the List interface, so they share many methods:

• add(element): Adds an element to the list.
• get(index): Retrieves element at a specific index.
• remove(index) or remove(object): Removes elements by index or object.
• size(): Returns the number of elements.
• contains(object): Checks if an element exists.

🚀 Conclusion

Both ArrayList and LinkedList are essential dynamic list implementations in Java. Choosing between them depends on your application's needs—whether you prioritize quick random access or frequent insertions/removals.

Understanding their differences helps you write efficient, performant Java code.