java把e盘中a文件夹里所有文件复制到d盘中b文件夹中

以下是Java实现该操作的代码：

import java.io.File;
import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.io.IOException;

public class FileCopyExample {
    public static void main(String[] args) {
        String sourceFolder = "E:/a";
        String destinationFolder = "D:/b";
        copyFolder(new File(sourceFolder), new File(destinationFolder));
        System.out.println("Files copied successfully!");
    }

    public static void copyFolder(File source, File destination) {
        if (source.isDirectory()) {
            if (!destination.exists()) {
                destination.mkdir();
            }

            String[] files = source.list();

            for (String file : files) {
                File srcFile = new File(source, file);
                File destFile = new File(destination, file);
                copyFolder(srcFile, destFile);
            }
        } else {
            FileInputStream inputStream = null;
            FileOutputStream outputStream = null;
            byte[] buffer = new byte[1024];

            try {
                inputStream = new FileInputStream(source);
                outputStream = new FileOutputStream(destination);
                int length;
                while ((length = inputStream.read(buffer)) > 0) {
                    outputStream.write(buffer, 0, length);
                }
            } catch (IOException e) {
                e.printStackTrace();
            } finally {
                try {
                    inputStream.close();
                    outputStream.close();
                } catch (IOException e) {
                    e.printStackTrace();
                }
            }
        }
    }
}

该代码会将E盘中的a文件夹中的所有文件和子文件夹复制到D盘中的b文件夹中。如果目标文件夹不存在，则会先创建该文件夹。在每个文件的复制过程中，会使用字节流的方式复制文件内容。最后，程序会输出“Files copied successfully!”的信息表示复制完成。