Tutorial Intro

Queues: A Queue (FIFO - First In, First Out) is a linear data structure where elements are inserted at the back (enqueue) and removed from the front (dequeue). It follows the principle that the element added first is the first to be removed. LinkedList: A LinkedList is a linear data structure where elements are not stored in contiguous memory locations. Each element (node) holds data and a reference to the next node in the list. This makes it efficient for insertions and removals at the beginning or end of the list.

LinkedList as a Queue Implementation

While Java provides the Queue interface, there's no concrete implementation class. LinkedList's characteristics (efficient insertions at the beginning and removals at the head) make it a suitable choice to emulate queue behavior. We can use LinkedList's methods to mimic enqueue and dequeue operations for a queue-like functionality. Points ⮚ We treat the LinkedList's head as the front of the queue and the tail as the back. ⮚ Enqueue operations involve adding elements to the end (tail) of the LinkedList. ⮚ Dequeue operations involve removing elements from the beginning (head) of the LinkedList.

Implementation with Example

linkedlist as a queue example in Java import java.util.LinkedList; import java.util.Queue; public class Main { public static void main(String[] args) { Queue<String> fruitsQueue = new LinkedList<String>(); // Add elements to the queue fruitsQueue.add("Apple"); fruitsQueue.offer("Mango"); fruitsQueue.add("Banana"); fruitsQueue.offer("Orange"); System.out.println("Queue after adding elements: " + fruitsQueue); // Remove elements from the queue String removedFruit1 = fruitsQueue.remove(); String removedFruit2 = fruitsQueue.poll(); System.out.println("Removed elements: " + removedFruit1 +" & " + removedFruit2); System.out.println("Queue after removing elements: " + fruitsQueue); // Retrieve the element at the front of the queue String frontFruit1 = fruitsQueue.element(); String frontFruit2 = fruitsQueue.peek(); System.out.println("Front element of the queue using element(): " + frontFruit1); System.out.println("Front element of the queue using peek(): " + frontFruit2); // Iterate over the queue System.out.println("Iterating over the queue:"); for (String fruit : fruitsQueue) { System.out.println(fruit); } } }

Output

Queue after adding elements: [Apple, Mango, Banana, Orange] Removed elements: Apple & Mango Queue after removing elements: [Banana, Orange] Front element of the queue using element(): Banana Front element of the queue using peek(): Banana Iterating over the queue: Banana Orange

Advantages

⮚ Efficient enqueue and dequeue operations (O(1) average time complexity). ⮚ Dynamic size adjustment as elements are added or removed.

Disadvantages

⮚ Random access (accessing elements by index) is inefficient (O(n) time complexity). ⮚ Not thread-safe by default (requires additional synchronization for concurrent access).

Conclusion

While Java doesn't have a built-in LinkedListQueue class, you can effectively use LinkedList to implement queue behavior. It's a good choice when you need a simple queue with efficient insertions and removals at the beginning or end. However, for thread-safety or frequent random access, consider using a specialized queue implementation like ArrayDeque from the Java collections framework.

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