[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/Triangle.md

@@ -0,0 +1,46 @@
+
+
+# Triangle
+
+## oneOf schemas
+* [EquilateralTriangle](EquilateralTriangle.md)
+* [IsoscelesTriangle](IsoscelesTriangle.md)
+* [ScaleneTriangle](ScaleneTriangle.md)
+
+## Example
+```java
+// Import classes:
+import org.openapitools.client.model.Triangle;
+import org.openapitools.client.model.EquilateralTriangle;
+import org.openapitools.client.model.IsoscelesTriangle;
+import org.openapitools.client.model.ScaleneTriangle;
+
+public class Example {
+    public static void main(String[] args) {
+        Triangle exampleTriangle = new Triangle();
+
+        // create a new EquilateralTriangle
+        EquilateralTriangle exampleEquilateralTriangle = new EquilateralTriangle();
+        // set Triangle to EquilateralTriangle
+        exampleTriangle.setActualInstance(exampleEquilateralTriangle);
+        // to get back the EquilateralTriangle set earlier
+        EquilateralTriangle testEquilateralTriangle = (EquilateralTriangle) exampleTriangle.getActualInstance();
+
+        // create a new IsoscelesTriangle
+        IsoscelesTriangle exampleIsoscelesTriangle = new IsoscelesTriangle();
+        // set Triangle to IsoscelesTriangle
+        exampleTriangle.setActualInstance(exampleIsoscelesTriangle);
+        // to get back the IsoscelesTriangle set earlier
+        IsoscelesTriangle testIsoscelesTriangle = (IsoscelesTriangle) exampleTriangle.getActualInstance();
+
+        // create a new ScaleneTriangle
+        ScaleneTriangle exampleScaleneTriangle = new ScaleneTriangle();
+        // set Triangle to ScaleneTriangle
+        exampleTriangle.setActualInstance(exampleScaleneTriangle);
+        // to get back the ScaleneTriangle set earlier
+        ScaleneTriangle testScaleneTriangle = (ScaleneTriangle) exampleTriangle.getActualInstance();
+    }
+}
+```
+
+