Updated Code Style (markdown)

Code-Style.md

@@ -287,9 +287,31 @@ public class MyClass {
 }
 ```
 
+[`org.springframework.lang.Contract` annotation](https://docs.spring.io/spring-framework/docs/6.2.0-SNAPSHOT/javadoc-api/org/springframework/lang/Contract.html) can be used to specify some aspects of the method behavior depending on the arguments that are then [taken in account by NullAway](https://github.com/uber/NullAway/wiki/Supported-Annotations#contracts). See for example how `@Contract` is used in Spring Framework codebase in the `Assert` class:
+```java
+public abstract class Assert {
+	// ...
+	@Contract("false, _ -> fail")
+	public static void state(boolean expression, String message) {
+		if (!expression) {
+			throw new IllegalStateException(message);
+		}
+	}
+	// ...
+	@Contract("null, _ -> fail")
+	public static void notNull(@Nullable Object object, String message) {
+		if (object == null) {
+			throw new IllegalArgumentException(message);
+		}
+	}
+	// ...
+}
+```
+
+Those contract allows NullAway static analysis to understand that after an invocation of `Assert.state(value != null, "Value must not be null")` or `Assert.notNull(value, "Value must not be null")`, a nullable `value` can be considered as non nullable.
+
 Related guidelines:
  - When overriding a method, null-safety annotations of the super method need to be specified on the overridden method unless you want to override null-safety.
- - [`org.springframework.lang.Contract` annotation](https://docs.spring.io/spring-framework/docs/6.2.0-SNAPSHOT/javadoc-api/org/springframework/lang/Contract.html) can be used to specify some aspects of the method behavior depending on the arguments.
  - Use `@SuppressWarnings("NullAway")` when NullAway triggers irrelevant errors, which can happen due to [NullAway bugs or missing features](https://github.com/uber/NullAway/issues) or when the analysis is not able to prove null-safety (can happen with lambdas).
 
 ### Use of @Override