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 = /

package com.mkyong.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 : /Users/mkyong/Documents/workspace/maven/fileUtils/newFile.txt
File is created!

2. new File()

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

package com.mkyong.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 : /Users/mkyong/Documents/workspace/maven/fileUtils/newFile.txt
File is created!

3. Manual file separator

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

package com.mkyong.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("Done");
		} else {
			System.out.println("File already exists!");
		}

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

Output

Final filepath : /Users/mkyong/Documents/workspace/maven/fileUtils/newFile.txt
File is created!

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?