Use LinkedList instead of ArrayList

src/OrderMatching.java

@@ -2,8 +2,8 @@ import java.util.*;
 
 public class OrderMatching {
 
-	ArrayList<SellOrder> sellOrderQueue = new ArrayList<>();
-	ArrayList<BuyOrder> buyOrderQueue = new ArrayList<>();
+	List<SellOrder> sellOrderQueue = new LinkedList<>();
+	List<BuyOrder> buyOrderQueue = new LinkedList<>();
 	
 	/*
 	 * Checks if the order is valid
@@ -11,4 +11,5 @@ public class OrderMatching {
 	boolean validate(Order order) {		
 		return order.getQty() > 0 && order.getPrice() > 0.0;
 	}
+	
 }