File.separator and new File() in Java

In this tutorial, we'll look at three examples for building a path to a file:

File.separator or System.getProperty("file.separator")
File file = new File(path, filename)
Create a path manually (not recommended)

File.separator

This is the classic way to construct a path using File.separator or System.getProperty("file.separator"). Both will check the operating system used and return the file path correctly, for example:

1. Windows = \

2. Unix; Linux or Mac = /

import java.io.File; 
import java.io.IOException; 

public class FileSeparator {
 public static void main(String[] args) {
 try {

 String filename = "nouveau_fichier.txt"; 
 String currentdirectory= System.getProperty("user.dir"); 
 
 String absoluteFilePath = ""; 
 
 absoluteFilePath = currentdirectory + File.separator + filename; 

 System.out.println("Absolute Path: " + absoluteFilePath); 
 
 File file = new File(absoluteFilePath); 

 if (file.createNewFile()) {
 System.out.println("File created!"); 
 } else {
 System.out.println("File already exists."); 
 }

 } catch (IOException e) {
 e.printStackTrace(); 
 }
 }
}

Output:

Absolute path: C:\Documents and Settings\Poste07\workspace\File\nouveau_fichier.txt
File created!

new File()

Calling new File() also allows you to build the path of the file.

import java.io.File; 
import java.io.IOException; 

public class NewFile {
 public static void main(String[] args) {
 try {

 String filename = "nouveau_fichier.txt"; 
 String currentdirectory = System.getProperty("user.dir"); 
 
 File file = new File(currentdirectory, filename); 
 
 System.out.println("Path: " + file.getAbsolutePath()); 
 if (file.createNewFile()) {
 System.out.println("File created!"); 
 } else {
 System.out.println("File already exists."); 
 }

 } catch (IOException e) {
 e.printStackTrace(); 
 }
 }
}

Output:

Path: C:\Documents and Settings\Poste07\workspace\File\nouveau_fichier.txt
File already exists.

Build the path manually

This method is to be avoided, here we show you just to show all the ways to build a path.

import java.io.File; 
import java.io.IOException; 

public class NewFile {
 public static void main(String[] args) {
 try {

 String filename = "nouveau_fichier.txt"; 
 String currentdirectory = System.getProperty("user.dir"); 
 
 String AbsolutePath = ""; 
 String os = System.getProperty("os.name").toLowerCase(); 
 
 if (os.indexOf("win") >= 0) {
 
 //if windows
Absolutepath = currentdirectory + "\\" + filename; 
 
 } else if (os.indexOf("nix") >= 0 || 
 os.indexOf("nux") >= 0 || 
 os.indexOf("mac") >= 0) {
 
 //if unix or mac 
AbsolutePath = currentDirectory + "/" + filename; 
 
 }else{
 //os not found
AbsolutePath = currentdirectory + "/" + filename; 
 }

 System.out.println("Path: " + AbsolutePath); 
 
 File file = new File(AbsolutePath); 

 if (file.createNewFile()) {
 System.out.println("File created"); 
 } else {
 System.out.println("File already existing"); 
 }

 } catch (IOException e) {
 e.printStackTrace(); 
 }
 }
}

Output:

Path: C:\Documents and Settings\Poste07\workspace\File\nouveau_fichier.txt
File already exists.

Resources:
http://java.sun.com/javase/6/docs/api/java/io/File.html