Understand the idea

Files are external resources and their operations can fail. The java.nio.file API works with Path values and provides convenient text methods. This example writes a temporary file in the execution environment, reads it, and removes it; it does not write a file on the reader computer.

Explore the details

File handling is an important part of any application.

Java has several methods for creating, reading, updating, and deleting files.

Java File Handling

The File class from the java.io package, allows us to work with files.

To use the File class, create an object of the class, and specify the filename or directory name:

The File class has many useful methods for creating and getting information about files. For example:

Modern File API — java.nio.file.Files

Since Java 7, java.nio.file.Files provides a cleaner, more powerful file API with less boilerplate than the old java.io approach.

import java.nio.file.Files;
import java.nio.file.Path;
import java.util.List;

// Write to a file (creates or overwrites)
Path file = Path.of("notes.txt");
Files.writeString(file, "Hello from NIO!");

// Read entire file as a String
String content = Files.readString(file);
System.out.println(content);         // Hello from NIO!

// Read all lines as a List
List<String> lines = Files.readAllLines(file);
lines.forEach(System.out::println);

// Check if file exists
if (Files.exists(file)) {
    System.out.println("File size: " + Files.size(file) + " bytes");
}

// Delete the file
Files.deleteIfExists(file);

You will learn how to create, write, read and delete files in the next chapters:

A complete runnable example

This complete Main.java program focuses on the lesson idea. Reference fragments above may demonstrate individual statements; this example includes the imports, entry point, and supporting types it needs.

import java.nio.file.Files;
import java.nio.file.Path;
public class Main {
    public static void main(String[] args) throws Exception {
        Path file = Files.createTempFile("java-practice-", ".txt");
        try {
            Files.writeString(file, "Learning Java");
            System.out.println(Files.readString(file));
        } finally {
            Files.deleteIfExists(file);
        }
    }
}

Learning Java

Change it. Run it. Understand it.

Load this lesson example into the editor. Change one value or statement, predict the result, then press RUN to execute Java.

Make it your own

Your learning checkpoint

• Explain the example without reading the output first.
• Make the change requested in the practice task.
• Describe why the result changed—or why compilation failed.

Ready to move on? Follow the next lesson in course order, or return to the curriculum to review a prerequisite.