Java:如何定义从FileChannel读取所有数据的缓冲区大小

import java.io.File;
import java.io.FileInputStream;
import java.io.IOException;
import java.nio.ByteBuffer;
import java.nio.channels.FileChannel;

public class FileChannelExample {
    public static void main(String[] args) {
        File file = new File("path/to/file.txt");
        try (FileInputStream fis = new FileInputStream(file);
             FileChannel channel = fis.getChannel()) {
            int bufferSize = 1024; // 定义缓冲区大小为1024字节
            ByteBuffer buffer = ByteBuffer.allocate(bufferSize);

            int bytesRead;
            while ((bytesRead = channel.read(buffer)) != -1) {
                buffer.flip(); // 切换为读模式
                // 处理读取到的数据
                while (buffer.hasRemaining()) {
                    System.out.print((char) buffer.get());
                }
                buffer.clear(); // 清空缓冲区，准备下一次读取
            }
        } catch (IOException e) {
            e.printStackTrace();
        }
    }
}