How to construct a file path in Java

In this tutorial, we will show you three Java examples to construct a file path :

1. File.separator or System.getProperty(“file.separator”) (Recommended)
2. File file = new File(workingDir, filename); (Recommended)
3. Create the file separator manually. (Not recommend, just for fun)

1. File.separator

Classic Java example to construct a file path, using File.separator or System.getProperty("file.separator"). Both will check the OS and returns the file separator correctly, for example,

1. Windows = \
2. *nix or Mac = /

FilePathExample1.java

package com.favtuts.io.file;

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

public class FilePathExample1 {

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

            String filename = "newFile.txt";
            String workingDirectory = System.getProperty("user.dir");

            //****************//

            String absoluteFilePath = "";

            //absoluteFilePath = workingDirectory + System.getProperty("file.separator") + filename;
            absoluteFilePath = workingDirectory + File.separator + filename;

            System.out.println("Final filepath : " + absoluteFilePath);

            //****************//
                
            File file = new File(absoluteFilePath);

            if (file.createNewFile()) {
                System.out.println("File is created!");
            } else {
                System.out.println("File is already existed!");
            }
            
        } catch (IOException e) {
            e.printStackTrace();
        }

    }
    
}

Output

Final filepath : /java-core-tutorials-examples/newFile.txt
File is created!

2. new File()

Some developers are using new File() API to construct the file path.

FilePathExample2.java

package com.favtuts.io.file;

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

public class FilePathExample2 {

    public static void main(String[] args) {
        
        try {
            
            String filename = "newFile.txt";
		    String workingDirectory = System.getProperty("user.dir");

            //****************//
			
		    File file = new File(workingDirectory, filename);

            //****************//

            System.out.println("Final filepath : " + file.getAbsolutePath());
            if (file.createNewFile()) {
                System.out.println("File is created!");
            } else {
                System.out.println("File is already existed!");
            }

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

    }
    
}

Output

Final filepath : /java-core-tutorials-examples/newFile.txt
File is already existed!

3. Manual file separator

Check the system OS and create file path manually, just for fun, not recommend.

FilePathExample3.java

package com.favtuts.io.file;

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

public class FilePathExample3 {
    
    public static void main(String[] args) {
        
        try {
        
            String filename = "testing.txt";
            String workingDir = System.getProperty("user.dir");
                
            String absoluteFilePath = "";
    
            //****************//
                
            String your_os = System.getProperty("os.name").toLowerCase();
                
            if (your_os.indexOf("win") >= 0) {
                    
                //if windows
                absoluteFilePath = workingDir + "\\" + filename;
                    
            } else if (your_os.indexOf("nix") >= 0 || 
                               your_os.indexOf("nux") >= 0 || 
                               your_os.indexOf("mac") >= 0) {
                    
                //if unix or mac 
                absoluteFilePath = workingDir + "/" + filename;
                    
            }else{
                    
                //unknow os?
                absoluteFilePath = workingDir + "/" + filename;
                    
            }
    
            System.out.println("Final filepath : " + absoluteFilePath);
    
            //****************//
                
            File file = new File(absoluteFilePath);
    
            if (file.createNewFile()) {
                System.out.println("File is created!");
            } else {
                System.out.println("File already exists!");
            }
    
        } catch (IOException e) {
            e.printStackTrace();
        }

    }

}

Output

Final filepath : /java-core-tutorials-examples/testing.txt
File is created!

Download Source Code

$ git clone https://github.com/favtuts/java-core-tutorials-examples

$ cd java-io/file

References

1. File JavaDoc
2. How to get current working directory
3. How to detect os in Java
4. What os or arch value can I use?