# Queue

The `Queue` interface in Java represents a collection of elements where the order of elements is crucial. It follows the First-In-First-Out (FIFO) principle, meaning that the element that is added first is the one that is removed first. The `Queue` interface extends the `Collection` interface and is part of the `java.util` package.

#### Example:

```java
import java.util.LinkedList;
import java.util.Queue;

public class QueueExample {
    public static void main(String[] args) {
        Queue<String> queue = new LinkedList<>();

        // Adding elements to the queue
        queue.offer("Element 1");
        queue.offer("Element 2");
        queue.offer("Element 3");

        // Removing elements from the queue
        String removedElement = queue.poll();
        System.out.println("Removed Element: " + removedElement);

        // Peeking at the front element
        String frontElement = queue.peek();
        System.out.println("Front Element: " + frontElement);
    }
}
```

### 2. Deque Interface

The `Deque` interface (Double Ended Queue) extends the `Queue` interface and allows elements to be added or removed from both ends. It can function as both a queue and a stack. The `Deque` interface is also part of the `java.util` package.

#### Example:

```java
import java.util.ArrayDeque;
import java.util.Deque;

public class DequeExample {
    public static void main(String[] args) {
        Deque<String> deque = new ArrayDeque<>();

        // Adding elements to the front
        deque.addFirst("Element 1");
        deque.addFirst("Element 2");

        // Adding elements to the end
        deque.addLast("Element 3");

        // Removing elements from the front and end
        String removedFromFront = deque.removeFirst();
        String removedFromEnd = deque.removeLast();

        System.out.println("Removed from Front: " + removedFromFront);
        System.out.println("Removed from End: " + removedFromEnd);
    }
}
```

### Benchmark Performance Results:

Performance benchmarks for `Queue` and `Deque` operations depend on the specific implementation used (e.g., `LinkedList` for `Queue`, `ArrayDeque` for `Deque`). In general, operations such as adding and removing elements have constant time complexity.

### Brief Comparison Table:

<table data-full-width="false"><thead><tr><th>Feature</th><th>Queue</th><th>Deque</th></tr></thead><tbody><tr><td>Order</td><td>FIFO (First-In-First-Out)</td><td>Both FIFO and LIFO</td></tr><tr><td>Implementation</td><td>Usually LinkedList</td><td>Usually ArrayDeque</td></tr><tr><td>Methods</td><td><code>offer()</code>, <code>poll()</code>, <code>peek()</code></td><td><code>addFirst()</code>, <code>addLast()</code>, <code>removeFirst()</code>, <code>removeLast()</code>, <code>peekFirst()</code>, <code>peekLast()</code></td></tr></tbody></table>

### Summary:

* Use `Queue` when you need a simple FIFO structure.
* Use `Deque` when you need both FIFO and LIFO operations or need efficient insertion and removal at both ends.
* The choice between implementations (`LinkedList` or `ArrayDeque`) may depend on specific use cases and performance requirements.

Choose `Queue` for simple FIFO scenarios, and use `Deque` when you need more flexibility or efficiency in handling elements at both ends. The specific implementation may affect performance, so benchmarking in the context of your application is recommended.


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