How do I create a file and write to it in Java?

To create a file and write to it in Java, you can use either the traditional java.io classes or the modern java.nio.file API. Here are two common approaches:

1. Using java.io (FileWriter/BufferedWriter)

Steps:

• Use FileWriter or BufferedWriter for writing text.
• Wrap in a try-with-resources statement to ensure resources are closed automatically.
• Handle IOException.

Example:

import java.io.BufferedWriter;
import java.io.FileWriter;
import java.io.IOException;

public class WriteFileExample {
    public static void main(String[] args) {
        String content = "Hello, World!";
        String filePath = "example.txt";

        try (BufferedWriter writer = new BufferedWriter(new FileWriter(filePath))) {
            writer.write(content);
            System.out.println("File written successfully!");
        } catch (IOException e) {
            e.printStackTrace();
        }
    }
}

Notes:

• Default Encoding: FileWriter uses the platform’s default charset. For explicit encoding, use:

  new OutputStreamWriter(new FileOutputStream(filePath), StandardCharsets.UTF_8)

• Appending: Use new FileWriter(filePath, true) to append instead of overwrite.

2. Using java.nio.file (Files.write)

Steps:

• Use Files.write() from the NIO API for simplicity.
• Specify the file path (Path), content, and optional options (e.g., StandardOpenOption).

Example:

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

public class WriteFileNIOExample {
    public static void main(String[] args) {
        String content = "Hello, World!";
        Path path = Paths.get("example.txt");

        try {
            // Write bytes (converts String to UTF-8 bytes by default)
            Files.write(path, content.getBytes());

            // Or write lines (List<String>)
            // Files.write(path, Arrays.asList("Line 1", "Line 2"));

            System.out.println("File written successfully!");
        } catch (IOException e) {
            e.printStackTrace();
        }
    }
}

Notes:

• Charset: Specify encoding explicitly if needed:

  Files.write(path, content.getBytes(StandardCharsets.UTF_8));

• Options: Use StandardOpenOption.CREATE, StandardOpenOption.APPEND, etc.:

  Files.write(path, content.getBytes(), StandardOpenOption.APPEND);

• Create Directories: Ensure parent directories exist first:

  Path dir = Paths.get("myfolder");
  if (!Files.exists(dir)) {
      Files.createDirectories(dir);
  }

Key Differences

Feature	java.io (FileWriter)	java.nio.file (Files.write)
Simplicity	Requires more boilerplate.	Concise one-liner.
Encoding Control	Requires OutputStreamWriter for explicit encoding.	Supports charset via overloaded methods.
Appending	Use FileWriter(filePath, true).	Use StandardOpenOption.APPEND.
Exception Handling	Manual try-catch.	Manual try-catch.
Performance	Buffered writing is efficient for large data.	Optimized for simplicity and small writes.

Best Practices

• Use try-with-resources for java.io classes to prevent resource leaks.
• Prefer java.nio.file for modern code (simpler and more flexible).
• Handle exceptions (e.g., IOException, SecurityException).

Choose the method that best fits your use case and Java version!