diff --git a/src/main/java/Model/Share.java b/src/main/java/Model/Share.java
index dee79dd..92d6101 100644
--- a/src/main/java/Model/Share.java
+++ b/src/main/java/Model/Share.java
@@ -8,6 +8,22 @@ public class Share {
     private final BigDecimal purchasePrice;
 
     public Share(Stock stock, BigDecimal quantity, BigDecimal purchasePrice) {
+        if (stock == null) {
+            throw new IllegalArgumentException("Stock cannot be null");
+        }
+        if (quantity == null) {
+            throw new IllegalArgumentException("Quantity cannot be null");
+        }
+        if (quantity.compareTo(BigDecimal.ZERO) <= 0) {
+            throw new IllegalArgumentException("Quantity must be greater than zero");
+        }
+        if (purchasePrice == null) {
+            throw new IllegalArgumentException("Purchase price cannot be null");
+        }
+        if (purchasePrice.compareTo(BigDecimal.ZERO) < 0) {
+            throw new IllegalArgumentException("Purchase price cannot be negative");
+        }
+
         this.stock = stock;
         this.quantity = quantity;
         this.purchasePrice = purchasePrice;