From ad729436909692a86fffdd628f7bdc4d498fe93c Mon Sep 17 00:00:00 2001
From: SeonJae <dbtjswo4733@naver.com>
Date: Mon, 20 Nov 2017 15:57:27 +0900
Subject: [PATCH] Circular Queue

---
 Data Structures/Queues/RingQueue.java | 94 +++++++++++++++++++++++++++
 1 file changed, 94 insertions(+)
 create mode 100644 Data Structures/Queues/RingQueue.java

diff --git a/Data Structures/Queues/RingQueue.java b/Data Structures/Queues/RingQueue.java
new file mode 100644
index 000000000000..b240207899ce
--- /dev/null
+++ b/Data Structures/Queues/RingQueue.java	
@@ -0,0 +1,94 @@
+public interface Queue {
+
+	public void add(Object object);
+
+	public Object first();
+
+	public Object remove();
+
+	public int size();
+
+}
+public class RingQueue implements Queue {
+	private Object[] objArray = null;
+	private int size;
+	private int front;
+	private int rear;
+
+	public RingQueue(int n) {
+		// Create an array of size n
+		objArray = new Object[n];
+		size = 0;
+		front = 0;
+		rear = 0;
+	}
+
+	@Override
+	public void add(Object obj) {
+		// type obj if there is empty space in the queue
+		// if there is no empty space in the queue throw new IllegalStateException ("The queue is full");
+		if (size == objArray.length)
+			throw new IllegalStateException("The queue is full");
+
+		else {
+			rear = (rear + 1) % objArray.length;
+			objArray[rear] = obj;
+			size++;
+		}
+
+	}
+
+	@Override
+	public Object first() {
+		// return the first element if the queue is not empty
+		// if the queue is empty throw new IllegalStateException ("The queue is empty");
+		if (size == 0)
+			throw new IllegalStateException("The queue is empty");
+
+		return objArray[(front + 1) % objArray.length];
+	}
+
+	@Override
+	public Object remove() {
+		// If the queue is not empty, delete the first element and return
+		// if the queue is empty throw new IllegalStateException ("The queue is empty");
+		Object object = new Object();
+
+		if (size == 0)
+			throw new IllegalStateException("The queue is empty");
+
+		else {
+			front = (front + 1) % objArray.length;
+			object = objArray[front];
+
+			size--;
+		}
+		return object;
+	}
+
+	@Override
+	public int size() {
+		// returns the number of elements stored in the queue
+		return size;
+	}
+
+	@Override
+	public String toString() {
+		StringBuffer sb = new StringBuffer();
+
+		if (objArray == null)
+			return sb.toString();
+
+		if (front == rear)
+			return sb.toString();
+
+		int tempFront = front;
+		do {
+			tempFront = (tempFront + 1) % objArray.length;
+			sb.append(objArray[tempFront]);
+		} while (tempFront != rear);
+
+		return sb.toString();
+	}
+
+}