Mastering Java File Paths: Relative, Absolute & Canonical Methods

1. Introduction

In Java development we often need to obtain file paths, for example to read configuration files. This article discusses file paths and how to read files.

2. File Paths

File paths are usually either relative paths or absolute paths.

2.1 Relative Path

A relative path is resolved based on the location of the current file. In Java code the reference point is the location of the running code; as long as the referenced file’s position relative to the source file does not change, it can be read.

2.2 Absolute Path

An absolute path is the real location of a file in the file system, starting from the root directory (a drive letter on Windows). It is like giving a house number; the exact location can be found without additional context.

2.3 Path Shortcuts

Common shortcut symbols (using Unix‑like systems as example):

Symbol

Description

../

Parent directory of the current directory

./

Current directory

/

Root directory

~

User home directory (e.g., /Users/username on mac, c:\users\username on Windows)

On Windows the separator / is usually replaced by \ .

3. Reading Files in Java

Assume the following project structure:

foo
|_src
   |_Test.java
   |_app.yml

Test.java

contains the logic to read app.yml. Java provides java.io.File and three common methods to obtain a file’s path.

3.1 getPath()

Returns the abstract pathname as a string, i.e., the path passed to the File constructor. If the File was created with a relative path, getPath() returns a relative path; otherwise it returns an absolute path.

File file = new File("./app.yml");
System.out.println("path = " + file.getPath()); // path = ./app.yml

File file = new File("/Users/dax/IdeaProjects/foo/src/app.yml");
System.out.println("path = " + file.getPath()); // path = /Users/dax/IdeaProjects/foo/src/app.yml

3.2 getAbsolutePath()

Returns the absolute path of the file. Note that the path is resolved relative to the compiled location of the class, and shortcut symbols are not expanded.

File file = new File("./app.yml");
System.out.println("absolutePath = " + file.getAbsolutePath());
// absolutePath = /Users/dax/IdeaProjects/foo/./app.yml

Because shortcuts are not expanded, the same file can have many different absolute path representations.

3.3 getCanonicalPath()

Resolves the path by eliminating shortcuts and symbolic links, returning a unique canonical path. This operation accesses the file system and may be slower, so use it only when you need the exact location.

File file = new File("./app.yml");
System.out.println("canonicalPath = " + file.getCanonicalPath());
// canonicalPath = /Users/dax/IdeaProjects/foo/app.yml

A normalized path (without shortcuts) is unique for a fixed file location.