Java - Composing String pathnames doesn't work

When manipulating the pathnames of files and directories in String format, I use the convention that all directories pathnames ends with File.separator. This gives me an easy in-system way to differentiate between files and directories, and also allow me to compose pathnames very easily.

Java however doesn't follow this convention. This means that every time I acquire the pathname of a directory from somewhere, I need to check if it ends with File.separator and, if not, add the string to the pathname. Seems easy, right?

I can't manage to make it work.

The method pathOfCurrentDirectory() finds the directory of the program that starts the JVM and returns its absolute pathname with File.separator at the end. The method createLogFile() uses the previous method to create the absolute pathname of the log file, creates the missing directory if needed, creates the file, and then returns its absolute pathname.

The checks in pathOfCurrentDirectory() make it looks like its output truly ends with File.separator as intended. The checks in createLogFile() make it seem like it does not. What is happening?

	public static String createLogFile() {
		String pathOfCurrentDirectory = pathOfCurrentDirectory();
		String logDirectory = pathOfCurrentDirectory + "Log" + File.separator;
		System.out.println();
		System.out.println("pathOfCurrentDirectory: " + pathOfCurrentDirectory
					+ "\n logDirectory = " + logDirectory);
		String path = logDirectory + "Log_" + LogUtilities.dateId() + ".log";
		System.out.println("logFile: " + path + "\n logFile.exists() = " + new File(path).exists());
		
		FilesUtility.createNewFile(new File(path));
		System.out.println("After creation, logFile.exists() = " + new File(path).exists());
		
		return path;
	}
	public static String pathOfCurrentDirectory() {
		String output = new File(System.getProperty("user.dir")).getAbsolutePath();
	//	System.out.println("Dir: " + output);
	//	System.out.println("File.separatorChar = " + File.separatorChar);
		System.out.println("Last char of dir: " + output.charAt(output.length()-1));
		System.out.println("modifiedDir = " + (output + File.separator));
		String newOutput = (output + File.separator);
		System.out.println("newOutput = " + newOutput);
		//	return output;
		if( output.charAt(output.length()-1) == File.separatorChar )
			 return newOutput;
		else return output; 
	}

Java has 2 classes specifically for manipulating pathnames - File and Path, if you use these you will hardly ever need to use File.separator and risk String handling errors.

This shows using both File and Path:

public static void main(String[] args) throws IOException
{
    Files.createDirectories(Path.of(pathOfCurrentDirectory(), "Log"));
    File f = createLogAsFile();
    Path p = createLogAsPath();
}
private static Path createLogAsPath() throws IOException
{
    Path path = Path.of(pathOfCurrentDirectory(), "Log", "Log_" + LogUtilities.dateId() + ".log");
    System.out.println("createLogAsPath " + path + "\nFiles.isRegularFile(path) = " + Files.isRegularFile(path));
    Files.createFile(path);
    System.out.println("After creation, Files.isRegularFile(path) = " +Files.isRegularFile(path));
    return path;
}
private static File createLogAsFile() throws IOException
{
    File logDirectory = new File(pathOfCurrentDirectory(), "Log");
    File path = new File(logDirectory, "Log_" + LogUtilities.dateId() + ".log");
    System.out.println("createLogAsFile: " + path + "\n logFile.exists() = " + path.exists());
    path.createNewFile();
    System.out.println("After creation, logFile.exists() = " +path.exists());
    return path;
}
public static String pathOfCurrentDirectory() {
    return System.getProperty("user.dir");
}

Whether you use the File or Path version would depend on you other code thoug they are easy to switch between with toPath or toFile calls.

You can really replace your createLogFile() with

String filename = String.format("Log_%s.log", LogUtilities.dateId());
Path logfile = Paths.get("Log", filename); 
FilesUtility.createNewFile(logfile.toFile());