Java NIO Path

This tutorial is part of the Java NIO tutorial series. In this tutorial, we will see about what is a Path and a File with respect to Java NIO. Path is step one in files and IO processing. Files are stored in a disk or some media based on a file system. Tree structure based file system is popularly prevalent in current day operating systems. Tree structure starts with a root node and branches. There can be multiple root nodes (C:, D:) as we have in Windows.

A path can be used to identify and locate a file in the file system. There are two types of paths, relative and absolute. Absolute path is self sufficient, that is a file can be located with an absolute path without any other information. So the absolute path starts with the root node and ends with the file name identifier. In case of relative path, we need to combine it with another path to get the absolute path to locate the file.

java.nio.file.Path

java.nio.file.Path is an interface and it is used to represent a system dependent file path which can be used to locate a file in a file system.

How to create a file Path?

Following is an example way to instantiate a file (relative) path, “lib” is a directory name relative to current directory and “nio.jar” is a file name in that directory.

//import java.nio.file.FileSystems;
//import java.nio.file.Path;
Path path = FileSystems.getDefault().getPath("lib", "nio.jar");

Following is another example to instantiate a file (absolute) path.

//import java.nio.file.Path;
//import java.nio.file.Paths;
Path filePath = Paths.get("/etc/user/foo");

NOTE: Paths.get is a convenience method for FileSystems.getDefault().getPath. So the same code can be written as FileSystems.getDefault().getPath("/etc/user/foo");

Get Current Path

To get the current working directory with NIO, we can use the following code and it returns absolute path of current working directory.

	Path currentDirectory = Paths.get("").toAbsolutePath();

Join Paths – resolve

To join two paths in NIO, we can use the resolve method. If an absolute path is passed as parameter to resolve method, then the same is returned.

// In Windows OS
Path path1 = Paths.get("C:\\Users\\Java\\examples");
// Output is C:\Users\Java\examples\Test.java
System.out.println(path1.resolve("Test.java"));

Bridge Paths – relativize

In NIO, when we want to construct a Path from one location to another we can use the method relativize. This can be used to navigate between two paths.

Path path1 = Paths.get("C:\\Users");
Path path2 = Paths.get("C:\\Users\\Java\\examples");
// outcome is Java\examples
Path path1_to_path2 = path1.relativize(path2);
// outcome is ..\..
Path path2_to_path1 = path2.relativize(path1);

Remove Redundancies in Path – normalize

When we want to redundant information from Path, NIO provides the normalize method. In popular file systems, current directory is denoted by “.” and the parent directory by “..”. These notations can be present in a path. If we want to remove these notations from the Path and converts it.

		//normalize
		Path path5 = Paths.get("C:\\Users\\Java\\.\\examples");	
		//output C:\Users\Java\examples
		System.out.println(path5.normalize());		
		//output C:\Users\examples
		Path path6 = Paths.get("C:\\Users\\Java\\..\\examples");
		System.out.println(path6.normalize());	

Java NIO Path Example Program

package com.javapapers.java.nio;

import java.nio.file.FileSystems;
import java.nio.file.Path;
import java.nio.file.Paths;

public class PathFileNIO {
	public static void main(String... strings) {
		// instantiate a relative path
		Path p1 = FileSystems.getDefault().getPath("lib", "nio.jar");

		// instantiate a absolute path - windows OS
		Path p2 = Paths.get("C:\\Users\\Java\\examples");

		// get current working directory
		Path currentDirectory = Paths.get("").toAbsolutePath();
		System.out.println(currentDirectory.toAbsolutePath());

		// resolve path in Windows OS
		Path path1 = Paths.get("C:\\Users\\Java\\examples");
		// Output is C:\Users\Java\examples\Test.java
		System.out.println(path1.resolve("Test.java"));

		// relativize
		Path path3 = Paths.get("C:\\Users");
		Path path4 = Paths.get("C:\\Users\\Java\\examples");
		// outcome is Java\examples
		Path path3_to_path4 = path3.relativize(path4);
		System.out.println(path3_to_path4);
		// outcome is ..\..
		Path path4_to_path3 = path4.relativize(path3);
		System.out.println(path4_to_path3);
		
		//normalize
		Path path5 = Paths.get("C:\\Users\\Java\\.\\examples");	
		//output C:\Users\Java\examples
		System.out.println(path5.normalize());		
		//output C:\Users\examples
		Path path6 = Paths.get("C:\\Users\\Java\\..\\examples");
		System.out.println(path6.normalize());		
	}
}