NBKRIST JavaHub - NIO.2 Insights (with Diagram)

Expert View — NIO.2
In enterprise development, NIO.2 became indispensable: it offers robust file operations, safer error reporting, and powerful directory traversal. I used Path/Files in production systems for log rotation, file-based configuration, and safe atomic moves. Learn NIO.2 early — it simplifies real-world tasks and makes systems more resilient.

Quick Intro

Java NIO.2 (introduced in Java 7) modernizes file handling with the java.nio.file API. Core types: Path — represents a path; Files — utility operations for reading/writing/copying/deleting; FileSystem — abstraction over the OS file system.

1. Creating & Writing a File (NIO.2)

// Files.writeString(Path.of("example.txt"), "NBKRIST: NIO.2 sample");


import java.nio.file.*;
import java.io.IOException;

public class CreateFileNio {
  public static void main(String[] args) throws IOException {
    Path p = Path.of("example.txt");
    Files.writeString(p, "NBKRIST: NIO.2 sample");
    System.out.println("Created and wrote example.txt");
  }
}

2. Reading from a File


import java.nio.file.*;
import java.io.IOException;

public class ReadFileNio {
  public static void main(String[] args) throws IOException {
    Path p = Path.of("example.txt");
    String s = Files.readString(p);
    System.out.println("Content: " + s);
  }
}

3. Directory Traversal (DirectoryStream)

// DirectoryStream<Path> stream = Files.newDirectoryStream(Path.of("."));


import java.nio.file.*;
import java.io.IOException;

public class ListDirNio {
  public static void main(String[] args) throws IOException {
    try (DirectoryStream stream = Files.newDirectoryStream(Path.of("."))) {
      for (Path p : stream) System.out.println(p.getFileName());
    }
  }
}

4. Copy / Move / Atomic Operations


import java.nio.file.*;
import java.io.IOException;

public class CopyMoveNio {
  public static void main(String[] args) throws IOException {
    Path src = Path.of("example.txt");
    Path backup = Path.of("backup_example.txt");
    Files.copy(src, backup, StandardCopyOption.REPLACE_EXISTING);
    System.out.println("Copied to backup_example.txt");
  }
}

💡 Tip: NIO.2 operations provide better error messages and options (e.g., atomic move, replace existing) — prefer them in production code.

Why NIO.2 beats legacy java.io.File

Path / Files are more expressive and utility-driven than java.io.File.
Better exception handling and descriptive IOExceptions.
Support for file attributes, symbolic links, and file system providers (e.g., ZIP FS).
Convenient read/write helpers (Files.readString/writeString).

Practice Questions

1. Which core types are used in NIO.2 for file operations?

2. How do you quickly read or write small text files?

3. How to ensure move/copy replaces the target atomically?

Key Takeaways

Use Path to describe locations and Files to perform operations.
NIO.2 is the modern, recommended API for file handling in Java (since Java 7).
Prefer NIO.2 for production — it offers robust features and clearer semantics.
Practice listing, copying, and reading/writing using Files and DirectoryStream.