Comparing the Java Deque and Stack Data Structures

Deque vs. Stack in Java

In computer science, a deque (pronounced "deck") is a linear collection of elements which allow users to perform insertion and removal operations.

The Deque interface is part of the Java Collections Framework, and provides methods for both adding and removing elements. The interface supports two strategies: First-in-first-out (FIFO) and Last-in-first-out (LIFO).

A stack is also a linear collection of elements, but it does not allow users to add or remove elements. Instead, the only operation allowed is “push”, which adds elements to the top of the stack. Elements must be removed from the stack in the reverse order in which they were added, following the Last-in-first-out (LIFO) strategy.

Both deque and stack are used to store elements in a sequence, and in many cases, their functions overlap. However, there are several differences between the two, which can help you decide which one to use for a particular task.

Memory Usage

Deques require more memory than stacks, because they need space to store additional information such as the index of the next element, the address of the previous element, etc. Stacks, on the other hand, don’t require as much memory, since the only additional information they need to store is a pointer to the top of the stack.

Operations

Compared to stacks, deques allow for more versatile operations. As mentioned, they support both FIFO and LIFO strategies, and in addition, they also allow for arbitrary insertions and removals. Stacks, on the other hand, only allow for push and pop operations.

Performance

Stacks have better performance compared to deques. All operations in a stack take constant time, whereas insertion and removal operations in a deque can take linear time.