Java queue implementation

Examples

package com.w3schools;
 
public class Test {
    private int capacity;
    int queueArray[];
    int front = 0;
    int rear = -1;
    int currentSize = 0;
 
    public Test(int queueSize){
        this.capacity = queueSize;
        queueArray = new int[this.capacity];
    }
 
    /**
     * Adds element at the end of the queue.
     * @param item
     */
    public void enqueue(int item) {
        if (isQueueFull()) {
            System.out.println("Overflow state.");
        } else {
            rear++;
            if(rear == capacity-1){
                rear = 0;
            }
            queueArray[rear] = item;
            currentSize++;
            System.out.println("Element " + item+ " is pushed to Queue.");
        }
    }
 
    /**
     * Removes an element from the top of the queue
     */
    public void dequeue() {
        if (isQueueEmpty()) {
            System.out.println("Underflow state.");
        } else {
            front++;
            if(front == capacity-1){
                System.out.println("Removed element: "+queueArray[front-1]);
                front = 0;
            } else {
                System.out.println("Removed element: "+queueArray[front-1]);
            }
            currentSize--;
        }
    }
 
    /**
     * Checks whether the queue is full or not
     * @return boolean
     */
    public boolean isQueueFull(){
        boolean status = false;
        if (currentSize == capacity){
            status = true;
        }
        return status;
    }
 
    /**
     * Checks whether the queue is empty or not
     * @return
     */
    public boolean isQueueEmpty(){
        boolean status = false;
        if (currentSize == 0){
            status = true;
        }
        return status;
    }
 
	public static void main(String args[]){
	    try {
		Test queue = new Test(4);
	        queue.enqueue(41);
	        queue.dequeue();
	        queue.enqueue(6);
	        queue.enqueue(24);
	        queue.enqueue(7);
	        queue.dequeue();
	        queue.dequeue();
	        queue.enqueue(4);
	        queue.dequeue();
	        queue.enqueue(918);
		} catch (Exception e) {
			e.printStackTrace();
		}
	 }
}

package com.w3schools; public class Test { private int capacity; int queueArray[]; int front = 0; int rear = -1; int currentSize = 0; public Test(int queueSize){ this.capacity = queueSize; queueArray = new int[this.capacity]; } /** * Adds element at the end of the queue. * @param item */ public void enqueue(int item) { if (isQueueFull()) { System.out.println("Overflow state."); } else { rear++; if(rear == capacity-1){ rear = 0; } queueArray[rear] = item; currentSize++; System.out.println("Element " + item+ " is pushed to Queue."); } } /** * Removes an element from the top of the queue */ public void dequeue() { if (isQueueEmpty()) { System.out.println("Underflow state."); } else { front++; if(front == capacity-1){ System.out.println("Removed element: "+queueArray[front-1]); front = 0; } else { System.out.println("Removed element: "+queueArray[front-1]); } currentSize--; } } /** * Checks whether the queue is full or not * @return boolean */ public boolean isQueueFull(){ boolean status = false; if (currentSize == capacity){ status = true; } return status; } /** * Checks whether the queue is empty or not * @return */ public boolean isQueueEmpty(){ boolean status = false; if (currentSize == 0){ status = true; } return status; } public static void main(String args[]){ try { Test queue = new Test(4); queue.enqueue(41); queue.dequeue(); queue.enqueue(6); queue.enqueue(24); queue.enqueue(7); queue.dequeue(); queue.dequeue(); queue.enqueue(4); queue.dequeue(); queue.enqueue(918); } catch (Exception e) { e.printStackTrace(); } } }

Output

Element 41 is pushed to Queue.
Removed element: 41
Element 6 is pushed to Queue.
Element 24 is pushed to Queue.
Element 7 is pushed to Queue.
Removed element: 6
Removed element: 24
Element 4 is pushed to Queue.
Removed element: 7
Element 918 is pushed to Queue.