Add Circular Queue (#2528)

DataStructures/Queues/CircularQueue.java

@@ -0,0 +1,115 @@
+//This program implements the concept of CircularQueue in Java
+//Link to the concept: (https://en.wikipedia.org/wiki/Circular_buffer)
+
+public class CircularQueue {
+    public static void main(String[] args) {
+        circularQueue cq= new circularQueue(5);
+        System.out.println(cq.isEmpty());
+        System.out.println(cq.isFull());
+        cq.enQueue(1);
+        cq.enQueue(2);
+        cq.enQueue(3);
+        cq.enQueue(4);
+        cq.enQueue(5);
+
+        System.out.println(cq.deQueue());
+        System.out.println(cq.deQueue());
+        System.out.println(cq.deQueue());
+        System.out.println(cq.deQueue());
+        System.out.println(cq.deQueue());
+        System.out.println(cq.isFull());
+        System.out.println(cq.isEmpty());
+        cq.enQueue(6);
+        cq.enQueue(7);
+        cq.enQueue(8);
+        System.out.println(cq.peek());
+        System.out.println(cq.peek());
+        cq.deleteQueue();
+
+    }
+}
+class circularQueue{
+    int[] arr;
+    int topOfQueue;
+    int beginningOfQueue;
+    int size;
+    public circularQueue(int size){
+        arr=new int[size];
+        topOfQueue=-1;
+        beginningOfQueue=-1;
+        this.size=size;
+    }
+    public boolean isEmpty(){
+        if(beginningOfQueue==-1){
+            return true;
+        }else{
+            return false;
+        }
+    }
+
+    public boolean isFull(){
+        if(topOfQueue+1==beginningOfQueue){
+            return true;
+        }else if(topOfQueue==size-1 && beginningOfQueue==0){
+            return true;
+        }else{
+            return false;
+        }
+    }
+
+    public void enQueue(int value){
+        if(isFull()){
+            System.out.println("The Queue is full!");
+        }
+        else if(isEmpty()) {
+            beginningOfQueue=0;
+            topOfQueue++;
+            arr[topOfQueue]=value;
+            System.out.println(value+" has been successfully inserted!");
+        }else{
+            if(topOfQueue+1==size){
+                topOfQueue=0;
+            }else{
+                topOfQueue++;
+            }
+            arr[topOfQueue]=value;
+            System.out.println(value+" has been successfully inserted!");
+        }
+    }
+
+    public int deQueue(){
+        if(isEmpty()){
+            System.out.println("The Queue is Empty!");
+            return -1;
+        }else{
+            int res= arr[beginningOfQueue];
+            arr[beginningOfQueue]=Integer.MIN_VALUE;
+            if(beginningOfQueue==topOfQueue){
+                beginningOfQueue=topOfQueue=-1;
+            }else if(beginningOfQueue+1==size){
+                beginningOfQueue=0;
+            }else{
+                beginningOfQueue++;
+            }
+            return res;
+        }
+
+    }
+
+    public int peek(){
+        if(isEmpty()){
+            System.out.println("The Queue is Empty!");
+            return -1;
+        }else{
+            return arr[beginningOfQueue];
+        }
+    }
+
+    public void deleteQueue(){
+        arr=null;
+        System.out.println("The Queue is deleted!");
+    }
+
+}
+
+