Uses synchronised keyword.

os/code/os/src/main/java/com/scaler/producerconsumer/Consumer.java

@@ -12,15 +12,16 @@ public class Consumer implements Runnable {
     private Queue<UnitOfWork> store;
     private String name;
 
-
     @Override
     public void run() {
         while (true) {
+            synchronized (store) {
                 if (store.size() > 0) {
                     store.remove();
                     System.out.println("Consumed: " + name + " Left units :" + store.size());
                 }
             }
+        }
 
     }
 

os/code/os/src/main/java/com/scaler/producerconsumer/Producer.java

@@ -13,15 +13,16 @@ public class Producer implements Runnable {
     private int maxSize;
     private String name;
 
-
     @Override
     public void run() {
         while (true) {
+            synchronized (store) {
                 if (store.size() < maxSize) {
                     store.add(new UnitOfWork());
                     System.out.println("Produced: " + name + " Left units :" + store.size());
                 }
             }
+        }
 
     }