fixed race condition problem

Author: dlvsn

src/main/java/core/basesyntax/Counter.java

@@ -6,7 +6,7 @@
 public class Counter {
     private static final Logger logger = LogManager.getLogger(Counter.class);
     private static final String MESSAGE = "%20s, Thread # %2s, counter value %2d";
-    private int value;
+    private volatile int value;
 
     public Counter(int value) {
         this.value = value;

src/main/java/core/basesyntax/Main.java

@@ -1,10 +1,13 @@
 package core.basesyntax;
 
 public class Main {
-    public static void main(String[] args) {
+    public static void main(String[] args) throws InterruptedException {
         Counter counter = new Counter(20);
+        Thread a;
         for (int i = 1; i <= 20; i++) {
-            new MyThread(counter, String.valueOf(i)).start();
+            a = new MyThread(counter, String.valueOf(i));
+            a.start();
+            a.join();
         }
     }
 }