JAVA

java queue

import java.util.*;

Queue<Integer> queue = new LinkedList<Integer>();
// use non-primative types when constructing

// to add a value to the back of queue:
queue.add(7);

// to remove and return front value:
int next = queue.remove();

// to just return front value without removing:
int peek = queue.peek();

queue in java

queues, //add, remove, peek , size()
    Queue<Integer> q = new LinkedList<>();
	- Unlike stacks, a queue is open at both its ends. (one end enqueue & one end remove data, dequeue) FIFO
	- enqueue() − add (store) an item to the queue. 
	- dequeue() − remove (access) an item from the queue.
	- peek() − Gets the element at the front of the queue without removing it.
	- isfull() − Checks if the queue is full.
	- isempty() − Checks if the queue is empty.
      
      Queue<Integer> queue = new LinkedList<Integer>();
        queue.add(10);
        queue.add(20);
        int a = queue.remove();
        int peek = queue.peek();
        System.out.println(queue + " " + a); //[20] 10

Java Queue Implementation

import java.util.*;
public class Main {
    public static void main(String[] args) {
        Queue<Integer> q1 = new LinkedList<Integer>();
        //Add elements to the Queue
        q1.add(10);
        q1.add(20);
        q1.add(30);
        q1.add(40);
        q1.add(50);
        System.out.println("Elements in Queue:"+q1);
        //remove () method =>removes first element from the queue
        System.out.println("Element removed from the queue: "+q1.remove());
        //element() => returns head of the queue
        System.out.println("Head of the queue: "+q1.element());
        //poll () => removes and returns the head
        System.out.println("Poll():Returned Head of the queue: "+q1.poll());
        //returns head of the queue
        System.out.println("peek():Head of the queue: "+q1.peek());
        //print the contents of the Queue
        System.out.println("Final Queue:"+q1);
    }
}

Java How to use Queue?

// LinkedList implementation of Queue
Queue<String> animal1 = new LinkedList<>();

// Array implementation of Queue
Queue<String> animal2 = new ArrayDeque<>();

// Priority Queue implementation of Queue
Queue<String> animal 3 = new PriorityQueue<>();

Java Queue

The Queue interface is available in java.util package and extends the Collection interface. The queue collection is used to hold the elements about to be processed and provides various operations like the insertion, removal etc. It is an ordered list of objects with its use limited to insert elements at the end of the list and deleting elements from the start of list i.e. it follows the FIFO or the First-In-First-Out principle.

LinkedList, ArrayBlockingQueue and PriorityQueue are the most frequently used implementations.   

queue in java

//this a basic one 
public class prosses {
    int [] s;
    int quu;
    int tu;
  
    prosses () {//constructor
        s = new int[20];
        quu = -1;
        tu = 0;
    }
  
    void enqueue (int d) {//for input and prosses
        if (quu >= 19) {
            System.out.println("stack is full");
        } else {
            s[++quu] = d;

        }
    }
  
    int dequeue(){//to send the output
        if(quu<0 && quu>19 && tu<0 && tu>19) {
            System.out.println("not possible");
            return 'n';
        }

        return s[tu++];
    }
}