Create Queue.java

algorithms/data-structures/Queue.java

@@ -0,0 +1,99 @@
+// Java program for array
+// implementation of queue
+
+// A class to represent a queue
+class Queue {
+	int front, rear, size;
+	int capacity;
+	int array[];
+
+	public Queue(int capacity)
+	{
+		this.capacity = capacity;
+		front = this.size = 0;
+		rear = capacity - 1;
+		array = new int[this.capacity];
+	}
+
+	// Queue is full when size becomes
+	// equal to the capacity
+	boolean isFull(Queue queue)
+	{
+		return (queue.size == queue.capacity);
+	}
+
+	// Queue is empty when size is 0
+	boolean isEmpty(Queue queue)
+	{
+		return (queue.size == 0);
+	}
+
+	// Method to add an item to the queue.
+	// It changes rear and size
+	void enqueue(int item)
+	{
+		if (isFull(this))
+			return;
+		this.rear = (this.rear + 1)
+					% this.capacity;
+		this.array[this.rear] = item;
+		this.size = this.size + 1;
+		System.out.println(item
+						+ " enqueued to queue");
+	}
+
+	// Method to remove an item from queue.
+	// It changes front and size
+	int dequeue()
+	{
+		if (isEmpty(this))
+			return Integer.MIN_VALUE;
+
+		int item = this.array[this.front];
+		this.front = (this.front + 1)
+					% this.capacity;
+		this.size = this.size - 1;
+		return item;
+	}
+
+	// Method to get front of queue
+	int front()
+	{
+		if (isEmpty(this))
+			return Integer.MIN_VALUE;
+
+		return this.array[this.front];
+	}
+
+	// Method to get rear of queue
+	int rear()
+	{
+		if (isEmpty(this))
+			return Integer.MIN_VALUE;
+
+		return this.array[this.rear];
+	}
+}
+
+
+public class Test {
+	public static void main(String[] args)
+	{
+		Queue queue = new Queue(1000);
+
+		queue.enqueue(10);
+		queue.enqueue(20);
+		queue.enqueue(30);
+		queue.enqueue(40);
+
+		System.out.println(queue.dequeue()
+						+ " dequeued from queue\n");
+
+		System.out.println("Front item is "
+						+ queue.front());
+
+		System.out.println("Rear item is "
+						+ queue.rear());
+	}
+}
+