update doc, samples

Author: wing328

docs/generators/java.md

@@ -12,6 +12,7 @@ sidebar_label: java
 |artifactId|artifactId in generated pom.xml. This also becomes part of the generated library's filename| |openapi-java-client|
 |artifactUrl|artifact URL in generated pom.xml| |https://github.com/openapitools/openapi-generator|
 |artifactVersion|artifact version in generated pom.xml. This also becomes part of the generated library's filename| |1.0.0|
+|asyncNative|If true, async handlers will be used, instead of the sync version| |false|
 |bigDecimalAsString|Treat BigDecimal values as Strings to avoid precision loss.| |false|
 |booleanGetterPrefix|Set booleanGetterPrefix| |get|
 |caseInsensitiveResponseHeaders|Make API response's headers case-insensitive. Available on okhttp-gson, jersey2 libraries| |false|