feat: 배열 기반 Queue peek 메소드 예제코드 구현

Author: ksundong

yoonexample/src/main/java/queue/ArrayQueue.java

@@ -49,7 +49,11 @@ public E dequeue() {
 
   @Override
   public E peek() {
-    return null;
+    if (isEmpty()) {
+      throw new EmptyQueueException();
+    }
+
+    return (E) queueArray[nextIndex(this.front)];
   }
 
   private int nextIndex(int pos) {