How to check on field in JSON for null?

I have below JSON response in which I need to check whether response field has null value or not. If response field has null value then I need to exit out of the program.

[
    {
        "results": {
            "response": null,
            "type": "ABC"
        },
        "error": null
    }
]

What is the easiest way to check this out? One option I know is to convert JSON to POJO and then check response field. Is there any other way?