Add Queue using LinkedList

Author: bcExpt1123

src/main/java/org/alda/Main.java

@@ -11,6 +11,8 @@
 import org.alda.structure.linkedList.sorted.SortedLinkedList;
 import org.alda.structure.queue.IQueue;
 import org.alda.structure.queue.Queue;
+import org.alda.structure.queue.array.QueueArray;
+import org.alda.structure.queue.linkedList.QueueLinkedList;
 import org.alda.structure.stack.array.IStackArray;
 import org.alda.structure.stack.array.StackArray;
 import org.alda.structure.stack.linkedList.IStackLinkedList;
@@ -123,11 +125,61 @@ public static void testQueue(){
         intQueue.enqueue(5);
 
         Integer item = intQueue.dequeue();
+        Integer item1 = intQueue.dequeue();
+        Integer item2 = intQueue.dequeue();
 
         Integer front = intQueue.front();
         Integer rear = intQueue.rear();
 
         System.out.println(item);
+        System.out.println(item1);
+        System.out.println(item2);
+        System.out.println(front);
+        System.out.println(rear);
+    }
+
+    public static void testQueueArray(){
+        IQueue<Integer> intQueue = new QueueArray<>();
+
+        intQueue.enqueue(1);
+        intQueue.enqueue(2);
+        intQueue.enqueue(3);
+        intQueue.enqueue(4);
+        intQueue.enqueue(5);
+
+        Integer item = intQueue.dequeue();
+        Integer item1 = intQueue.dequeue();
+        Integer item2 = intQueue.dequeue();
+
+        Integer front = intQueue.front();
+        Integer rear = intQueue.rear();
+
+        System.out.println(item);
+        System.out.println(item1);
+        System.out.println(item2);
+        System.out.println(front);
+        System.out.println(rear);
+    }
+
+    public static void testQueueLinkedList(){
+        IQueue<Integer> intQueue = new QueueLinkedList<>();
+
+        intQueue.enqueue(1);
+        intQueue.enqueue(2);
+        intQueue.enqueue(3);
+        intQueue.enqueue(4);
+        intQueue.enqueue(5);
+
+        Integer item = intQueue.dequeue();
+        Integer item1 = intQueue.dequeue();
+        Integer item2 = intQueue.dequeue();
+
+        Integer front = intQueue.front();
+        Integer rear = intQueue.rear();
+
+        System.out.println(item);
+        System.out.println(item1);
+        System.out.println(item2);
         System.out.println(front);
         System.out.println(rear);
     }

src/main/java/org/alda/structure/queue/linkedList/QueueLinkedList.java

@@ -0,0 +1,85 @@
+package org.alda.structure.queue.linkedList;
+
+import org.alda.structure.linkedList.simple.Node;
+import org.alda.structure.queue.IQueue;
+
+import java.util.ArrayList;
+
+/**
+ * @author bcExpt1123
+ *
+ * Implementation of a generic Queue using a LinkedList.
+ * @param <T>
+ */
+public class QueueLinkedList<T> implements IQueue<T> {
+
+    public Node<T> front;
+    public Node<T> rear;
+
+
+    public QueueLinkedList() {
+        front = null;
+        rear = null;
+    }
+
+    /**
+     * {@inheritDoc}
+     * @return
+     */
+    public boolean isEmpty() {
+        return front == null;
+    }
+
+    /**
+     * {@inheritDoc}
+     * @param item the item to be added.
+     */
+    public void enqueue(T item) {
+        Node<T> newNode = new Node<>(item);
+        if (rear == null) {
+            front = newNode;
+            rear = newNode;
+        } else {
+             rear.next = newNode;
+             rear = newNode;
+        }
+    }
+
+    /**
+     * {@inheritDoc}
+     * @return
+     */
+    public T dequeue() {
+        T popped = null;
+        if (!isEmpty()) {
+            popped = front.data;
+            front = front.next;
+            if (front == null) {
+                rear = null;
+            }
+        }
+        return popped;
+    }
+
+    /**
+     * {@inheritDoc}
+     * @return
+     */
+    public T front() {
+        if (isEmpty()) {
+            return null;
+        }
+        return front.data;
+    }
+
+    /**
+     * {@inheritDoc}
+     * @return
+     */
+    public T rear(){
+        if (isEmpty()) {
+            return null;
+        }
+        return rear.data;
+    }
+}