How to find resource id of a file located in /res/raw folder by its filename?

I want to get the resource id of the file located in /res/raw folder by filename. I have tried the following 2 methods but both of them return resource id as 0(zero).

Method 1:

String filename = "abc.txt";
int id = getResources().getIdentifier(filename, "raw", getPackageName());

Method 2:

String filename = "abc.txt";
String fullyQualifiedName = getPackageName() + ":raw/" + filename;
int id = getResources().getIdentifier(fullyQualifiedName, null, null);

If this is not the correct way, then how do we get the resource id by filename located in raw folder in Android.

Drop the extension:

String filename = "abc";
int id = getResources().getIdentifier(filename, "raw", getPackageName());