Unable to write string data into ORC file (or at least read it back)

I'm trying to create a little utility to convert CSV files into ORC files. I've noticed that the resulting ORC files don't seem quite correct, though. In an effort to create a simple reproducible test case, I just changed the "Writing/Reading ORC Files" examples here:

https://orc.apache.org/docs/core-java.html

to create a file based on a pair of strings instead of integers. Basically I changed the loop as follows:

        BytesColumnVector first = (BytesColumnVector) writeBatch.cols[0];
        BytesColumnVector last = (BytesColumnVector) writeBatch.cols[1];
        for (int r = 0; r < 10; ++r)
        {
            String firstName = ("First-" + r).intern();
            String lastName = ("Last-" + (r * 3)).intern();
            ...
        }

The file writes without errors, and if I write it with no compression, I can see the data using strings my-file.orc. However, when I then try to read the data back from the file and print out the resulting batches to the console, I get the following:

["       ", "      "]
["       ", "      "]
["       ", "      "]
["       ", "      "]
["       ", "       "]
["       ", "       "]
["       ", "       "]
["       ", "       "]
["       ", "       "]
["       ", "       "]

I've been completely unable to find any documentation or example code that would help me to understand why this isn't working. Any insights about what I may be doing wrong here would be greatly appreciated!