给定一个文件夹，无论其内有没有文件或文件夹，也无论有多少层，都可以实现文件夹的复制Java代码，需要用到递归运算方法

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

public class Demo {

    public static void main(String[] args) {
        copy(new File(D:\\desktop\\temp), new File(D:\\desktop\\abc));

    }
    
    public static void copy(File file, File target) {
        target = new File(target, file.getName());
        if (!target.exists()) target.mkdirs();
        if (file.isDirectory()) {
            File[] files = file.listFiles();
            for (File f : files) {
                if (f.isDirectory()) copy(f, target);
                else copyFile(f, target);
            }
        } else {
            copyFile(file, target);
        }
    }

    public static void copyFile(File file, File directory) {
        try {
            FileInputStream input = new FileInputStream(file);
            FileOutputStream output = new FileOutputStream(new File(directory, file.getName()));
            byte[] buff = new byte[8192];
            int len = -1;
            while ((len = input.read(buff))  -1) {
                output.write(buff);
            }
            input.close();
            output.close();
        } catch (Exception e) {

        }
    }

}