Create Queue.java

Queue.java

@@ -0,0 +1,98 @@
+// Queue implementation in Java
+
+public class Queue {
+  int SIZE = 5;
+  int items[] = new int[SIZE];
+  int front, rear;
+
+  Queue() {
+    front = -1;
+    rear = -1;
+  }
+
+  boolean isFull() {
+    if (front == 0 && rear == SIZE - 1) {
+      return true;
+    }
+    return false;
+  }
+
+  boolean isEmpty() {
+    if (front == -1)
+      return true;
+    else
+      return false;
+  }
+
+  void enQueue(int element) {
+    if (isFull()) {
+      System.out.println("Queue is full");
+    } else {
+      if (front == -1)
+        front = 0;
+      rear++;
+      items[rear] = element;
+      System.out.println("Inserted " + element);
+    }
+  }
+
+  int deQueue() {
+    int element;
+    if (isEmpty()) {
+      System.out.println("Queue is empty");
+      return (-1);
+    } else {
+      element = items[front];
+      if (front >= rear) {
+        front = -1;
+        rear = -1;
+      } /* Q has only one element, so we reset the queue after deleting it. */
+      else {
+        front++;
+      }
+      System.out.println("Deleted -> " + element);
+      return (element);
+    }
+  }
+
+  void display() {
+    /* Function to display elements of Queue */
+    int i;
+    if (isEmpty()) {
+      System.out.println("Empty Queue");
+    } else {
+      System.out.println("\nFront index-> " + front);
+      System.out.println("Items -> ");
+      for (i = front; i <= rear; i++)
+        System.out.print(items[i] + "  ");
+
+      System.out.println("\nRear index-> " + rear);
+    }
+  }
+
+  public static void main(String[] args) {
+    Queue q = new Queue();
+
+    // deQueue is not possible on empty queue
+    q.deQueue();
+
+    // enQueue 5 elements
+    q.enQueue(1);
+    q.enQueue(2);
+    q.enQueue(3);
+    q.enQueue(4);
+    q.enQueue(5);
+
+    // 6th element can't be added to because the queue is full
+    q.enQueue(6);
+
+    q.display();
+
+    // deQueue removes element entered first i.e. 1
+    q.deQueue();
+
+    // Now we have just 4 elements
+    q.display();
+
+  }
+}