Queues

In Java, a Queue is an abstract data type that is used to store and process elements in a first-in, first-out (FIFO) manner. It is similar to a line of people waiting to buy tickets at a movie theater, where the person who arrives first will be the first to buy a ticket and leave the line.

What is a Queue?

A Queue is a linear data structure that allows elements to be added and removed only from the ends of the queue. It operates on the principle of first-in, first-out (FIFO), which means that the element that is inserted first will be the first one to be removed.

When to use Queue?

Queues are used in situations where we need to handle data in a FIFO manner, such as when processing tasks or events that arrive in a specific order. Some common examples of using queues include handling tasks in a multi-threaded environment, implementing a message queue, and processing events in real-time systems.

How Queue differs from Stack?

A Queue is different from a Stack, which is another abstract data type used to store and process elements. In a Stack, elements are added and removed from the top of the stack in a last-in, first-out (LIFO) manner. In a Queue, elements are added and removed from the ends of the queue in a first-in, first-out (FIFO) manner.

How to Implement a Queue in Java?

There are several ways to implement a Queue in Java. One way is to use the built-in Queue interface in the Java Collections framework. Another way is to implement a Queue from scratch using an array or a linked list.

Here is an example of implementing a Queue using the built-in Queue interface.

Main


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


public class MyQueue {
    private Queue<String> queue = new LinkedList<>();

    public void enqueue(String element) {
        queue.add(element);
    }

    public String dequeue() {
        return queue.poll();
    }

    public boolean isEmpty() {
        return queue.isEmpty();
    }

    public int size() {
        return queue.size();
    }
}

In the above example, we create a class MyQueue that uses the built-in Queue interface and the LinkedList class to implement a queue. We provide methods to add an element to the end of the queue (enqueue), remove an element from the front of the queue (dequeue), check if the queue is empty (isEmpty()), and get the size of the queue (size()).

Advantages of Using Queues	Disadvantages of Using Queues
Provides a simple and efficient way to store and process elements in a FIFO manner.	Can be inefficient when used in situations where elements need to be inserted or removed from the middle of the queue.
Allows easy implementation of complex algorithms, such as breadth-first search and topological sorting.	Can be limited in size, depending on the available memory.
Can be used in a variety of applications, such as job scheduling, message passing, and real-time systems.

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