Merge pull request #813 from Sandunifernando/patch-5

Create QeueArrayApp.java for users in hacktober2021

Program's_Contributed_By_Contributors/Java_Programs/Misc/QeueArrayApp.java

@@ -0,0 +1,124 @@
+package packageDA;
+
+public class QeueArrayApp {
+
+	public static void main(String[] args) {
+		// TODO Auto-generated method stub
+		QueueArray x = new QueueArray(5);
+		x.display();
+		x.enqueue(2);
+		x.enqueue(8);
+		x.enqueue(3);
+		x.display();
+		try {
+		    x.dequeue();
+		    x.display();
+		    x.enqueue(23);
+	    	x.enqueue(45);
+		    x.enqueue(59);
+		    x.enqueue(89);
+		    x.display();
+		    x.dequeue();
+		    x.display();
+		    x.enqueue(89);
+		    x.display();
+		    System.out.println("Peek is "+x.peek());
+		} catch(Exception e) {
+		    System.out.println(e.toString());
+		}
+
+	}
+
+}
+
+
+class QueueArray{
+    private int maxSize;
+    private int[] queArray;
+    private int front;
+    private int rear;
+    private int nItems;
+
+    public QueueArray(int S) {
+        this.queArray = new int[S];
+        this.maxSize = S;
+        this.front=0;
+        this.rear=-1;
+        this.nItems=0;
+    }   
+
+    public boolean isEmpty() {
+        return this.nItems == 0;
+    }
+
+    public boolean isFull() {
+        return this.nItems == this.maxSize;
+    }
+
+    public int size() {
+        return this.nItems;
+    }
+
+    public void enqueue(int value){
+        if(isFull()){
+            System.out.println("Queue is full cannot enqueue");
+            return;
+        }
+
+        /*if(this.rear == this.maxSize -1) {
+            this.rear =0;
+        }else {
+            this.rear++;
+        }*/
+
+        rear = (rear + 1) % maxSize;
+        this.queArray[rear] = value;
+        this.nItems++;
+
+    }
+
+    public int dequeue() throws Exception{
+        if(isEmpty()){
+            throw new Exception("Queue is empty cannot remove");
+        }
+
+        int removedItem = this.queArray[front];
+        /*if(this.front == this.maxSize -1) {
+            this.front =0;
+        }else {
+            front++;
+        }*/
+
+        front = (front + 1) % maxSize;
+        nItems--;
+        return removedItem;
+    }
+
+    public int peek() throws Exception{
+        if(isEmpty()){
+            throw new Exception("Queue is empty cannot remove");
+        }
+        return this.queArray[this.front];
+    }
+
+    public void display(){
+        if(isEmpty()){
+            System.out.println("Queue is empty nothing to print");
+            return;
+        }
+
+        int i = this.front;
+        while(i != rear) {
+            System.out.print(this.queArray[i] + " ");
+            /*if(i == maxSize -1) {
+                i=0;
+            } else {
+                i++;
+            }*/
+            i = (i + 1) % maxSize;
+        }
+
+        System.out.print(this.queArray[rear]);
+        System.out.println();
+    }
+}