Replace path constructions using separator char

Find ALL occurrences where we construct a file path using

• File.separatorChar
• System.getProperty("file.separator")

and string concatenation like for example when creating a FileInputStream

FileInputStream fis = new FileInputStream(appDataDir + System.getProperty("file.separator")
+ DatabaseUtil.ORDER_ENTRY_UPGRADE_SETTINGS_FILENAME);

and replace the construction of the file path with proper use of Java's Path constructor which can easily do this for us, like so

FileInputStream fis = new FileInputStream(Paths.get("a", "b", "c").toFile());

To clarify:
The task is to replace the string concatenation with proper use of Java's Paths class which can construct paths for us. The above code sample is just an example from the code base, this task does not mean you need to replace anything with FileInputStream.