jni types conversion

I am working on an android project with native code that is supposed to update a List and some other boolean variables in an object.

consider the following code

some java class in my code looks like:

 class ReturnObject
{
    boolean a, b;
    public List<String[]> listA;

}

public class foo
{
    public native void someFunction(ReturnObject returnObject);
}

and the native code looks like:

JNIEXPORT void JNICALL Java_com_example_androidtest_TestActivity_someFunction
  (JNIEnv * env, jobject jObj, jobject returnObject) {
    std::string f = "foo";
    // missing code here
    // returnObject.add(f) // add like in java
}

How can I set the values of the boolean variables?

and for the the List (knowing my data in the native code are stored as std::string ), how can I invoke add(String[] string) method of the List class from native code?