How Can I Efficiently Skip the Byte Order Mark (BOM) When Reading Files in Java?

Byte Order Mark (BOM) in Java can cause problems when reading files

For those code writers who write BOM to their file format Say, BOM is useful. However, when it comes to reading these files, especially for a platform-independent language like Java, the situation can be complicated.

To skip the BOM, follow these steps:

1. Get the FileSystem of the file system using Path#getFileSystem() with the java.nio package.
2. Get the FileSystemProvider from the file system that is used to read and write the root directory of the file system.
3. Create a StreamOpener to handle the BOM.
4. Open the FileChannel using the provided StreamOpener.

Here is an example of how to skip the BOM and read the file:

import java.io.IOException;
import java.nio.file.FileSystems;
import java.nio.file.Files;
import java.nio.file.Path;
import java.nio.file.Paths;
import java.nio.file.StandardOpenOption;
import java.nio.file.StreamOpener;
import java.nio.channels.FileChannel;

public class SkipBOMExample {

    public static void main(String[] args) throws IOException {
        Path file = Paths.get("path/to/file.txt");
        FileSystem fs = FileSystems.getFileSystem(file.getFileSystem());
        FileSystemProvider provider = fs.provider();

        StreamOpener opener = (Path path, StandardOpenOption... options) -> {
            FileChannel channel = provider.newByteChannel(path, options);
            // 跳过3个字节（BOM的大小）
            channel.position(3);
            return channel;
        };

        try (FileChannel channel = Files.newByteChannel(file, StandardOpenOption.READ, opener)) {
            byte[] bytes = new byte[1024];
            while (channel.read(bytes) != -1) {
                // 处理读取到的字节
            }
        }
    }
}

By using this method you can skip when reading the file containing the BOM BOM and read the file contents accurately.

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