The following example will not throw a FileAlreadyExistsException:

    @Test
    public void testit() throws Exception {
        Path osFile = Path.of("Hello.txt");
        Files.deleteIfExists(osFile);
        Files.writeString(osFile, "Hello World");

        try (SeekableByteChannel srcCh = Files.newByteChannel(osFile, Set.of(CREATE_NEW))) {
            System.out.println("oops");
        }

        try (SeekableByteChannel srcCh = Files.newByteChannel(osFile, Set.of(CREATE_NEW, READ))) {
            System.out.println("oops");
        }
    }



If you specify Set.of(CREATE_NEW, WRITE) you will get the expected Exception