What are three invalid characters at the beginning of my file?

The first three bytes of a UTF-8 with BOM file is the byte order mark. By default, a Java file is created as UTF-8 with BOM.

You can change the current file’s encoding by going to File | Save As… and changing the Encoding to UTF-8 without Signature.

You can change the default encoding for the current configuration by going to Tools | Properties for Current Configuration, go to File, and click on New Files…. You can specify if you want to add a Unicode signature with the Add a Unicode Signature (BOM) checkbox.

New File Details