Java Files

Up to now your programs have kept everything in memory, which disappears when the program ends. Files change that. By reading from and writing to files, your program can save user data, load configuration, or process documents. Java has supported files since its earliest versions, and modern Java gives you cleaner tools through the java.nio.file package.

Two ways to work with files

Both approaches work, and you will see both in real codebases. The classic File class from java.io is still common in tutorials, while the Files helper class from java.nio.file offers convenient one-line methods for reading and writing. Learning both means you can read any Java code you come across.

import java.io.File;

public class Main {
  public static void main(String[] args) {
    File myFile = new File("notes.txt");

    if (myFile.exists()) {
      System.out.println("Name: " + myFile.getName());
      System.out.println("Path: " + myFile.getAbsolutePath());
      System.out.println("Writable: " + myFile.canWrite());
      System.out.println("Size in bytes: " + myFile.length());
    } else {
      System.out.println("The file does not exist yet.");
    }
  }
}

Creating a File object does not create a file on disk; it just represents a path. The exists() method tells you whether an actual file is there. This is why checking before you act is a good habit.

The modern Path and Files approach

import java.nio.file.Path;
import java.nio.file.Files;
import java.io.IOException;

public class Main {
  public static void main(String[] args) throws IOException {
    Path path = Path.of("notes.txt");

    if (Files.exists(path)) {
      System.out.println("File name: " + path.getFileName());
      System.out.println("Size: " + Files.size(path) + " bytes");
      System.out.println("Readable: " + Files.isReadable(path));
    } else {
      System.out.println("No such file.");
    }
  }
}

• A File or Path object only describes a location; it does not create the file.
• Use exists() to check whether a file is actually present before using it.
• java.io centres on the File class; java.nio.file centres on Path and the Files helper.
• Modern code generally prefers java.nio.file for its cleaner methods.