First, the loadFromArray() method:

    private void loadFromArray(){
        JsonArray array = BUILDERFACTORY.createArrayBuilder()
                .add(BUILDERFACTORY.createObjectBuilder()
                        .add("name", "User1")
                        .add("email", "[email protected]"))
                .add(BUILDERFACTORY.createObjectBuilder()
                        .add("name", "User2")
                        .add("email", "[email protected]"))
                .add(BUILDERFACTORY.createObjectBuilder()
                        .add("name", "User3")
                        .add("email", "[email protected]")) 
                .build(); 
        fromArray = jsonbBuilder.toJson(array);
    }

It uses the BuilderFactory and the createArrayBuilder method to easily build an array of JSONs (each call of createObjectBuilder creates another array member). At the end, we use the JSON-B to convert it to a JSON string:

    private void loadFromStructure(){
        JsonStructure structure = BUILDERFACTORY.createObjectBuilder()
                .add("name", "User1")
                .add("email", "[email protected]")
                .add("profiles", BUILDERFACTORY.createArrayBuilder()
                        .add(BUILDERFACTORY.createObjectBuilder()
                                .add("id", "1")
                                .add("name", "Profile1"))
                        .add(BUILDERFACTORY.createObjectBuilder()
                                .add("id", "2")
                                .add("name", "Profile2")))
                .build();
        fromStructure = jsonbBuilder.toJson(structure);

        JsonPointer pointer = new JsonPointerImpl("/profiles");
        JsonValue value = pointer.getValue(structure);
        fromJpointer = value.toString();
    }

Here, instead of an array, we are building a single JSON structure. Again, we use JSON-B to convert the JsonStructure to a JSON string.

We also took advantage of having this JsonStructure ready and used it to query the user profiles using the JsonPointer object:

private void loadFromUser(){
        User user = new User("Elder Moraes", "[email protected]",
                    new Integer[]{1,2,3});
        fromUser = jsonbBuilder.toJson(user);
    }

And here was the simplest: creating an object and asking JSON-B to convert it to a JSON string.