Fixed bugs.

src/main/ui/Main.java

@@ -15,6 +15,7 @@ public class Main {
         //options = new Options();
         System.out.println("Welcome to " + PROGRAM_NAME + "!");
         guess();
+        end();
     }
 
     // java main
@@ -40,8 +41,16 @@ public class Main {
 
     public int getUserInt() {
         Scanner scan = new Scanner(System.in);
-        int result = scan.nextInt();
-        scan.close();
+        int result = 0;
+        while (true) {
+            if (scan.hasNextInt()) {
+                result = scan.nextInt();
+                break;
+            } else {
+                System.out.println("Try again?");
+                scan.nextLine();
+            }
+        }
         return result;
     }