Null pointer exception when checking for permission with android.content.Context.checkPermission

I need to check for permissions before querying the Android calendar for events. To do it, Android studio is warning that I need to follow a check before querying. The auto generated code is this piece:

if (ActivityCompat.checkSelfPermission(this, Manifest.permission.READ_CALENDAR) != PackageManager.PERMISSION_GRANTED) {
        System.out.println("NO ACCESS TO CALENDAR!! Abort mission, abort mission!!");
    }

When trying to run it, I get this error:

Attempt to invoke virtual method 'int
android.content.Context.checkPermission(java.lang.String, int, int)' on a null object reference

So it is clear that something is null at this point, and I tried to get the context of the app with a different way, but it's still the same error. Other thing I tried was this code, which is supposed to handle the targets lower than Android 6:

if (ContextCompat.checkSelfPermission(this, Manifest.permission.READ_CALENDAR) != PackageManager.PERMISSION_GRANTED) {

        ActivityCompat.requestPermissions(this, new String[]{Manifest.permission.READ_CALENDAR},
                MY_PERMISSIONS_REQUEST_READ_CONTACTS);
    }

Still get the same error, can anybody help me with this?