Introduction

In Java, ArrayDeque is usually a better default than LinkedList when you need a queue, stack, or deque. Both support insertion and removal at the ends, but ArrayDeque tends to win in practice because it uses contiguous storage, creates less object overhead, and interacts with CPU caches more efficiently.

Same big-O, different real performance

For end operations, both structures offer effectively constant-time behavior:

• add to front or back
• remove from front or back
• peek at front or back

So the usual reason to prefer ArrayDeque is not asymptotic complexity. It is constant factors and memory behavior.

ArrayDeque stores data more compactly

ArrayDeque uses a resizable circular array. That means the elements live in a contiguous block of memory.

LinkedList stores each element in a separate node object, and each node also keeps references to its neighbors.

That creates extra overhead:

• more object allocations
• more pointer fields
• more garbage collection pressure

For ordinary queue workloads, that overhead usually buys you nothing useful.

Better cache locality

Contiguous arrays are friendlier to CPU caches than linked nodes scattered through memory. When iterating or repeatedly pushing and popping near the ends, ArrayDeque often benefits from better locality and fewer pointer hops.

This is one of the main reasons it tends to outperform LinkedList even when both have similar theoretical operation costs.

Example queue usage

1import java.util.ArrayDeque;
2import java.util.Deque;
3
4public class Demo {
5    public static void main(String[] args) {
6        Deque<Integer> queue = new ArrayDeque<>();
7        queue.addLast(10);
8        queue.addLast(20);
9        queue.addLast(30);
10
11        System.out.println(queue.removeFirst());
12        System.out.println(queue.peekFirst());
13    }
14}

For stack-style usage:

1Deque<String> stack = new ArrayDeque<>();
2stack.push("a");
3stack.push("b");
4System.out.println(stack.pop());

These are exactly the common use cases where ArrayDeque shines.

Why LinkedList is rarely the better queue

LinkedList is still valid Java, but it is usually not the best deque implementation unless you have a specific reason to need list-node semantics.

For example:

• if you need random indexed access, neither is ideal
• if you need a queue or stack, ArrayDeque is usually the better default
• if you specifically need list operations with node-like insertion patterns, LinkedList may still be relevant

Most code that uses LinkedList as a queue could switch to ArrayDeque and become simpler and faster.

ArrayDeque also forbids null

One useful design difference is that ArrayDeque does not allow null elements. That helps avoid ambiguity between:

• an actual stored value
• a sentinel meaning "no element"

For queue and stack code, that is often a feature rather than a limitation.

Resizing is usually not a problem

ArrayDeque can occasionally resize its internal array, which costs more than a normal push or pop. But this overhead is amortized and usually far cheaper than paying per-element linked-node overhead for the whole lifetime of the structure.

So while LinkedList does not resize a backing array, it often still loses overall due to poorer memory behavior.

Common Pitfalls

The most common mistake is comparing only big-O notation and concluding that LinkedList and ArrayDeque are interchangeable in practice. Another is choosing LinkedList as a queue just because it sounds like a structure built for insertions and removals. Developers also sometimes forget that ArrayDeque rejects null, which can break code that uses null as a sentinel. Using either structure when an entirely different abstraction is needed, such as a priority queue, is another common design error. Finally, people often benchmark tiny examples and miss how memory layout and allocation overhead dominate on larger real workloads.

Summary

• 'ArrayDeque is usually the best default for Java queue, stack, and deque workloads.'
• It uses a compact circular array instead of allocating linked nodes per element.
• Better cache locality and lower object overhead usually make it faster than LinkedList.
• 'LinkedList is rarely the better queue unless you need specific list-oriented behavior.'
• 'ArrayDeque does not allow null, which often improves API clarity.'
• Prefer ArrayDeque unless you have a concrete reason not to.