Paths and Files · File I/O in Java | Java

Paths and Files

The Modern File API

java.nio.file (Java 7+) is the modern way to work with files. A Path describes a location; the Files class has static methods that do the work.

Task	Method
Build a path	`Path.of("data", "orders.csv")`
Check existence	`Files.exists(path)`
Read all text	`Files.readString(path)`
Read lines	`Files.readAllLines(path)` / `Files.lines(path)`
Write text	`Files.writeString(path, text)`
Append	`Files.writeString(path, text, StandardOpenOption.APPEND)`
Copy / move / delete	`Files.copy`, `Files.move`, `Files.delete`, `Files.deleteIfExists`
Create folders	`Files.createDirectories(path)`
Size	`Files.size(path)`

Note: Almost every Files method throws the checked IOException, so you must catch it or declare throws IOException.

Working with Path

Example

A Path is only a description; creating one does not touch the disk.

import java.nio.file.Path;

public class Main {
    public static void main(String[] args) {
        Path p = Path.of("reports", "2024", "sales.csv");
        System.out.println("Path      : " + p.toString().replace('\\', '/'));
        System.out.println("File name : " + p.getFileName());
        System.out.println("Parent    : " + p.getParent().toString().replace('\\', '/'));
        System.out.println("Parts     : " + p.getNameCount());
        System.out.println("Absolute? : " + p.isAbsolute());
        Path sibling = p.resolveSibling("returns.csv");
        System.out.println("Sibling   : " + sibling.getFileName());
        Path messy = Path.of("reports/./2024/../2024/sales.csv").normalize();
        System.out.println("Normalized: " + messy.toString().replace('\\', '/'));
        System.out.println("CSV file? : " + p.getFileName().toString().endsWith(".csv"));
    }
}

Output

Path      : reports/2024/sales.csv
File name : sales.csv
Parent    : reports/2024
Parts     : 3
Absolute? : false
Sibling   : returns.csv
Normalized: reports/2024/sales.csv
CSV file? : true

Tip: Never build paths by concatenating strings with "/" or "\". Path.of and resolve use the right separator for Windows, Linux and macOS.