update example to use optional config

Author: zhongkechen

examples/src/main/java/software/amazon/lambda/durable/examples/WaitForConditionExample.java

@@ -5,6 +5,7 @@
 import java.util.concurrent.atomic.AtomicInteger;
 import software.amazon.lambda.durable.DurableContext;
 import software.amazon.lambda.durable.DurableHandler;
+import software.amazon.lambda.durable.config.WaitForConditionConfig;
 import software.amazon.lambda.durable.model.WaitForConditionResult;
 
 /**
@@ -21,17 +22,18 @@ public Integer handleRequest(Integer input, DurableContext context) {
         // Poll the shipment status until the order is shipped.
         // The check function simulates an order shipment status
         // which transitions from PENDING > PROCESSING > SHIPPED
-        return context.waitForCondition("wait-for-shipment", Integer.class, (callCount, stepCtx) -> {
-            // Simulate checking shipment status from an external service
-            if (callCount == null) {
-                callCount = 0;
-            }
-            if (callCount >= 3) {
-                // Order has shipped — stop polling
-                return WaitForConditionResult.stopPolling(callCount + 1);
-            }
-            // Order still processing — continue polling
-            return WaitForConditionResult.continuePolling(callCount + 1);
-        }); // Order pending - initial status
+        return context.waitForCondition(
+                "wait-for-shipment",
+                Integer.class,
+                (callCount, stepCtx) -> {
+                    // Simulate checking shipment status from an external service
+                    if (callCount >= 3) {
+                        // Order has shipped — stop polling
+                        return WaitForConditionResult.stopPolling(callCount + 1);
+                    }
+                    // Order still processing — continue polling
+                    return WaitForConditionResult.continuePolling(callCount + 1);
+                },
+                WaitForConditionConfig.<Integer>builder().initialState(0).build()); // Order pending - initial status
     }
 }