diff --git a/src/main/java/hu/bme/mit/spaceship/TorpedoStore.java b/src/main/java/hu/bme/mit/spaceship/TorpedoStore.java
index 76a3cea..08fcf46 100644
--- a/src/main/java/hu/bme/mit/spaceship/TorpedoStore.java
+++ b/src/main/java/hu/bme/mit/spaceship/TorpedoStore.java
@@ -14,8 +14,11 @@ public class TorpedoStore {
 
   private int torpedoCount = 0;
 
+  private Random generator;
+
   public TorpedoStore(int numberOfTorpedos){
     this.torpedoCount = numberOfTorpedos;
+    generator= new Random();
 
     // update failure rate if it was specified in an environment variable
     String failureEnv = System.getenv("IVT_RATE");
@@ -28,20 +31,24 @@ public TorpedoStore(int numberOfTorpedos){
     }
   }
 
+  /**
+   * @param numberOfTorpedos
+   * @return
+   */
   public boolean fire(int numberOfTorpedos){
     if(numberOfTorpedos < 1 || numberOfTorpedos > this.torpedoCount){
-      new IllegalArgumentException("numberOfTorpedos");
+      throw new IllegalArgumentException("numberOfTorpedos");
     }
 
     boolean success = false;
 
     // simulate random overheating of the launcher bay which prevents firing
-    Random generator = new Random();
+    
     double r = generator.nextDouble();
 
     if (r >= FAILURE_RATE) {
       // successful firing
-      this.torpedoCount =- numberOfTorpedos;
+      this.torpedoCount =this.torpedoCount- numberOfTorpedos;
       success = true;
     } else {
       // simulated failure