How to Efficiently Copy Files in Java without Manual Looping?

How to Efficiently Copy Files in Java without Manual Looping

Java's traditional file copying approach using stream handling and manual looping can be cumbersome. However, there are more concise alternatives within the language, particularly in the newer NIO (New Input/Output) package.

NIO introduces the transferTo() and transferFrom() methods in the FileChannel class. These methods provide a direct and efficient way to transfer data between files.

NIO-Based File Copying Code

import java.io.File;
import java.nio.channels.FileChannel;
import java.nio.file.Files;
import java.nio.file.StandardOpenOption;

public class FileCopierNIO {
  public static void copyFile(File sourceFile, File destFile) throws IOException {
    if (!destFile.exists()) {
      destFile.createNewFile();
    }

    try (
      FileChannel source = new FileInputStream(sourceFile).getChannel();
      FileChannel destination = new FileOutputStream(destFile).getChannel()
    ) {
      destination.transferFrom(source, 0, source.size());
      source.close();
      destination.close();
    }
  }

}

This code simplifies file copying to a single method call, eliminating the need for manual looping and stream handling. Moreover, it can be further simplified using the Files.copy() method from the NIO.2 package:

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

public class FileCopierNIO2 {
  public static void copyFile(File sourceFile, File destFile) throws IOException {
    Path sourcePath = sourceFile.toPath();
    Path destPath = destFile.toPath();
    Files.copy(sourcePath, destPath, StandardCopyOption.REPLACE_EXISTING);
  }
}

The Files.copy() method provides the same functionality as the FileChannel.transferFrom() method, but with a more concise syntax.

Benefits of NIO-Based Copying

The NIO-based approach to file copying offers several advantages over the traditional method:

• Improved Performance: NIO uses direct memory buffers and native system calls, resulting in faster data transfer speeds.
• Reduced Memory Overhead: By eliminating manual looping and buffering, NIO reduces the memory overhead associated with file copying.
• Simplified Code: The NIO-based code is more concise and easier to maintain than the traditional approach.

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