🆚 Stack vs ArrayDeque — Why ArrayDeque wins
1. ✅ Performance
| Feature | Stack | ArrayDeque |
|---|---|---|
| Underlying base | Vector (synchronized) | Resizable array (not synchronized) |
| Thread-safe? | Yes (but outdated style) | No (but faster in single-threaded use) |
| Performance | Slower due to synchronization | Faster — no sync overhead |
🔧
ArrayDequeavoids the cost of locking/unlocking thatStackinherits fromVector.
2. ✅ Cleaner, Modern API
ArrayDequeimplementsDeque, so you get stack and queue methods:
push(), pop(), peek(), addFirst(), addLast(), removeFirst(), removeLast()
Stack is limited to only:
push(), pop(), peek(), empty()
3. ✅ Better Design
Stack is a legacy class:
- Inherits from
Vector(a thread-safe, legacy list) - Brings in unwanted methods like
insertElementAt(),elementAt(), etc.
This goes against good object-oriented design — Stack has more methods than it should, violating encapsulation.
👉 ArrayDeque, by contrast, is a dedicated stack/queue structure with a clear, tight API.
4. ✅ No capacity limits or reallocation issues
Both Stack and ArrayDeque are resizable, but ArrayDeque is:
- Backed by an efficient circular array
- Dynamically grows without copying every element
It’s tuned for fast push/pop performance on both ends.
📜 Java Docs Recommendation
Official JavaDoc:
“This class is likely to be faster thanStackwhen used as a stack.”
📌 That’s why ArrayDeque is now the recommended stack replacement in modern Java.
🧪 Example: ArrayDeque as a Stack
Deque<String> stack = new ArrayDeque<>();
stack.push("A");
stack.push("B");
stack.push("C");
System.out.println(stack.pop()); // C