Question

I am working on different platforms (Solaris/Windows). I need to create a File object which contains several path elements. The question is: is it better to create the final File object “step by step” or in a single call. The latter one assumes that Java does the right path mapping on different platforms. Does it always do a correct mapping due to different file separators?

File parent = // some directory;

// Use several file objects...
File myFile1 = new File(new File(new File(parent, "part1"), "part2"), "myfile");

// .. or use just on (on all platforms!)?
File myFile2 = new File(parent, "part1/part2/myfile");

The first solution is probably (a) slower and (b) less readable…

Answer 1

Use the 2nd one, and instead of hard-coding the forward slash, use File.separatorChar / File.separator:

The system-dependent default name-separator character. This field is initialized to contain the first character of the value of the system property file.separator. On UNIX systems the value of this field is ‘/’; on Microsoft Windows systems it is ‘\’.

Note that you don’t need to do this with Sun’s JVM – the Win32FileSystem class translates forward to backward slashes – if you look at its code, it has slash and altSlash, and in case altSlash (/) is encountered, the class normalizes the path

But, as pointed in the comments, in order to remain confident that your code will be portable, use the File.separator