如何使用 Java NIO 将所有文件从源目录移动到目标目录，将现有文件保留在目标目录中？

Question

I am using Java 8 in Windows, I am trying to achieve one simple thing. Say I have a source directory and a destination directory. I am trying to move files from source to destination in a daily basis. Below is a simple java code, using NIO;

Path sourcePath = Paths.get("C:\\source");
Path destinationPath = Paths.get("C:\\destination");
try {
    Files.move(sourcePath, destinationPath, StandardCopyOption.REPLACE_EXISTING);
} catch (IOException e) {
    e.printStackTrace();
}

In the first run, this will work fine, because the destination is empty. On the second run, or if the destination is not empty, NIO will throw an exception;

java.nio.file.DirectoryNotEmptyException: C:\destination
    at sun.nio.fs.WindowsFileCopy.move(WindowsFileCopy.java:373)
    at sun.nio.fs.WindowsFileSystemProvider.move(WindowsFileSystemProvider.java:287)
    at java.nio.file.Files.move(Files.java:1395)
    at instacopy.Test.main(Test.java:14)

What I am trying to achieve is;

1. New files should be moved from source to destination.
2. If file with same name exists in destination, it should be replaced with the new one.

Is this possible? If yes, how can I do this?

Answer 1

first of all:

it would be a good idea to just test if folder is empty.

Anyway getting to the point in order to overwrite files in the dest: The best option IMO is to use apache commons.io FileUtils :

FileUtils.copyDirectory(srcDir, destDir);

then delete files in the source dir

FileUtils.copyDirectory desc: Copies a whole directory to a new location preserving the file dates.

This method copies the specified directory and all its childdirectories and files to the specified destination.The destination is the new location and name of the directory.

The destination directory is created if it does not exist.If the destination directory did exist, then this method mergesthe source with the destination, with the source taking precedence.

Another option using java nio - you would need to walk through the files and foreach file copy and overwrite

Paths target;
try (Stream<Path> paths = Files.walk(sourcePath)) {
                paths.forEach((srcPath)->{Files.copy(srcPath, target, StandardCopyOption.REPLACE_EXISTING);});
            } catch (IOException e) {
                e.printStackTrace();
            }

then delete files in the source dir