[java][native] Fix urlQuery string method in oneOf (#14488)

* better tests, fix oneOf in urlquery string method

* update samples

* update

samples/client/petstore/java/native-async/docs/NullableShape.md

@@ -0,0 +1,41 @@
+
+
+# NullableShape
+
+The value may be a shape or the 'null' value. The 'nullable' attribute was introduced in OAS schema >= 3.0 and has been deprecated in OAS schema >= 3.1.
+
+## oneOf schemas
+* [Quadrilateral](Quadrilateral.md)
+* [Triangle](Triangle.md)
+
+NOTE: this class is nullable.
+
+## Example
+```java
+// Import classes:
+import org.openapitools.client.model.NullableShape;
+import org.openapitools.client.model.Quadrilateral;
+import org.openapitools.client.model.Triangle;
+
+public class Example {
+    public static void main(String[] args) {
+        NullableShape exampleNullableShape = new NullableShape();
+
+        // create a new Quadrilateral
+        Quadrilateral exampleQuadrilateral = new Quadrilateral();
+        // set NullableShape to Quadrilateral
+        exampleNullableShape.setActualInstance(exampleQuadrilateral);
+        // to get back the Quadrilateral set earlier
+        Quadrilateral testQuadrilateral = (Quadrilateral) exampleNullableShape.getActualInstance();
+
+        // create a new Triangle
+        Triangle exampleTriangle = new Triangle();
+        // set NullableShape to Triangle
+        exampleNullableShape.setActualInstance(exampleTriangle);
+        // to get back the Triangle set earlier
+        Triangle testTriangle = (Triangle) exampleNullableShape.getActualInstance();
+    }
+}
+```
+
+