We've added Java 11 Native HTTP client (https://openjdk.java.net/groups/net/httpclient/intro.html) support to OpenAPI Generator (https://github.com/OpenAPITools/openapi-generator). To generate the Java API client (Java 11 HTTP Client) given an OpenAPI/Swagger specification file, please follow 3 simple steps below:<p>1. Download the Java JAR (https://oss.sonatype.org/content/repositories/snapshots/org/openapitools/openapi-generator-cli/4.1.0-SNAPSHOT/openapi-generator-cli-4.1.0-20190727.141928-68.jar)<p>2. Rename the JAR as "openapi-generator-cli.jar"<p>3. Run the following command to generate a Java API client for the Petstore API (https://raw.githubusercontent.com/OpenAPITools/openapi-generator/master/modules/openapi-generator/src/test/resources/2_0/petstore.yaml):<p>Mac/Linux:<p>> java -jar openapi-generator-cli.jar generate -g java -i https://raw.githubusercontent.com/OpenAPITools/openapi-generator/master/modules/openapi-generator/src/test/resources/2_0/petstore.yaml -o /var/tmp/java11/ --additional-properties library=native<p>Windows:<p>> java -jar openapi-generator-cli.jar generate -g java -i https://raw.githubusercontent.com/OpenAPITools/openapi-generator/master/modules/openapi-generator/src/test/resources/2_0/petstore.yaml -o C:\tmp\java11 --additional-properties library=native<p>Thanks Benjamin (https://github.com/bbdouglas) from Yelp (http://yelp.com/) for contributing the enhancement (https://github.com/OpenAPITools/openapi-generator/pull/3434).