When should I use File.separator and when File.pathSeparator?

Question

In the File class there are two strings, separator and pathSeparator.

What's the difference? When should I use one over the other?

Germanize

The naming is a bit confusing, the fast that something like this is needed is plain terrible (cf. Perl). Look at the examples for pathSeparatorChar and separatorChar. Or use the simple mnemonics: the pathSeparator separates paths. – Unglue

Taking a minute to print both of them to screen would have answered your question... – Pow

While I'd generally agree, simply printing them on his system isn't going to show the variants for other operating systems. – Fanya

Answer 1

If you mean File.separator and File.pathSeparator then:

• File.pathSeparator is used to separate individual file paths in a list of file paths. Consider on windows, the PATH environment variable. You use a ; to separate the file paths so on Windows File.pathSeparator would be ;.

• File.separator is either / or \ that is used to split up the path to a specific file. For example on Windows it is \ or C:\Documents\Test

Caretaker

Seems like File.separator should be File.fileSeparator regarding to File.pathSeparator – Willms

@Willms I see your point, but it might be redundant since the class name is File. I think the file part is implied. But who knows why they did a lot of what they did with Java. – Caretaker

IMO, splitting a file path on File.separator is an anti-pattern because Windows paths aren't required to use it (they can use forward slashes instead). – Clipfed

Answer 2

java.io.File class contains four static separator variables. For better understanding, Let's understand with the help of some code

1. separator: Platform dependent default name-separator character as String. For windows, it’s ‘\’ and for unix it’s ‘/’
2. separatorChar: Same as separator but it’s char
3. pathSeparator: Platform dependent variable for path-separator. For example PATH or CLASSPATH variable list of paths separated by ‘:’ in Unix systems and ‘;’ in Windows system
4. pathSeparatorChar: Same as pathSeparator but it’s char

Note that all of these are final variables and system dependent.

Here is the java program to print these separator variables. FileSeparator.java

import java.io.File;

public class FileSeparator {

    public static void main(String[] args) {
        System.out.println("File.separator = "+File.separator);
        System.out.println("File.separatorChar = "+File.separatorChar);
        System.out.println("File.pathSeparator = "+File.pathSeparator);
        System.out.println("File.pathSeparatorChar = "+File.pathSeparatorChar);
    }

}

Output of above program on Unix system:

File.separator = /
File.separatorChar = /
File.pathSeparator = :
File.pathSeparatorChar = :

Output of the program on Windows system:

File.separator = \
File.separatorChar = \
File.pathSeparator = ;
File.pathSeparatorChar = ;

To make our program platform independent, we should always use these separators to create file path or read any system variables like PATH, CLASSPATH.

Here is the code snippet showing how to use separators correctly.

//no platform independence, good for Unix systems
File fileUnsafe = new File("tmp/abc.txt");
//platform independent and safe to use across Unix and Windows
File fileSafe = new File("tmp"+File.separator+"abc.txt");

Creight

Note that in Java the backslash character actually is \\, because a single backslash is the escape character for other special character shorthands, so the backslash itself is used to escape itself. The String and char returned by the above-mentioned methods do return the properly formatted backslash (if on Windows). – Loferski

new File("tmp/abc.txt"); this is corectly for windows and linux but this is not corectly for unix new File("tmp\\abc.txt"); this is problem only unix – Frady

@Frady it is not quite clear in your comment, but are you conflating Linux and Unix? Because they are not the same :) – Steamtight

Answer 3

You use separator when you are building a file path. So in unix the separator is /. So if you wanted to build the unix path /var/temp you would do it like this:

String path = File.separator + "var"+ File.separator + "temp"

You use the pathSeparator when you are dealing with a list of files like in a classpath. For example, if your app took a list of jars as argument the standard way to format that list on unix is: /path/to/jar1.jar:/path/to/jar2.jar:/path/to/jar3.jar

So given a list of files you would do something like this:

String listOfFiles = ...
String[] filePaths = listOfFiles.split(File.pathSeparator);

Colorific

If you are building a *nix path like /var/temp then it's useless to use File.separator since you already have platform-dependent code. Might as well hardcode the path. – Godunov

@Godunov Yes I use File.separator less and less all the time. If you have a path generated and stored inside a file (or a database) that goes to another system, using File.separator on Win and then moving it to Linux will just cause a problem. Safer to just use "/". I was wondering if someone knows a reason to do otherwise but I don't see one here. – Goodsell