docs: swap examples used in readme (#408)

docs: document how to forcibly omit required field

Author: stainless-app[bot]

README.md

@@ -781,6 +781,21 @@ JsonValue complexValue = JsonValue.from(Map.of(
 ));
 ```
 
+Normally a `Builder` class's `build` method will throw [`IllegalStateException`](https://docs.oracle.com/javase/8/docs/api/java/lang/IllegalStateException.html) if any required parameter or property is unset.
+
+To forcibly omit a required parameter or property, pass [`JsonMissing`](openai-java-core/src/main/kotlin/com/openai/core/Values.kt):
+
+```java
+import com.openai.core.JsonMissing;
+import com.openai.models.ChatModel;
+import com.openai.models.chat.completions.ChatCompletionCreateParams;
+
+ChatCompletionCreateParams params = ChatCompletionCreateParams.builder()
+    .model(ChatModel.O3_MINI)
+    .messages(JsonMissing.of())
+    .build();
+```
+
 ### Response properties
 
 To access undocumented response properties, call the `_additionalProperties()` method: