[Pattern] Stack to Deque and ArrayDeque

[brunoborges]

Category

collections

Slug

stack-to-deque

Title

Stack to Deque and ArrayDeque

Difficulty

beginner

Since JDK

6

Summary

Use the Deque interface with ArrayDeque instead of the legacy Stack class.

Old code label

Legacy Stack

Old code

Stack<String> stack = new Stack<>();
stack.push("task");
String next = stack.pop();

Modern code label

Deque API

Modern code

Deque<String> stack = new ArrayDeque<>();
stack.push("task");
String next = stack.pop();

Explanation

Stack extends the legacy synchronized Vector class. Deque models stack operations directly, and ArrayDeque is the preferred general-purpose implementation for in-memory LIFO work.

Why the modern way wins

🎯 Better abstraction — Deque explicitly models both stack and queue operations.
⚡ Lower overhead — ArrayDeque avoids Vector's legacy synchronization.
🧩 More flexible — The same interface supports LIFO and FIFO algorithms.