FileUtils.copyDirectoryToDirectory(file, destination);

Files.createSymbolicLink(new File("/path/to/symlink").toPath(), new File("/path/to/destination".toPath())

java.nio.file.FileAlreadyExistsException: /home/nemtecl/Bureau/montest
    at java.base/sun.nio.fs.UnixException.translateToIOException(UnixException.java:94)
    at java.base/sun.nio.fs.UnixException.rethrowAsIOException(UnixException.java:111)
    at java.base/sun.nio.fs.UnixException.rethrowAsIOException(UnixException.java:116)
    at java.base/sun.nio.fs.UnixFileSystemProvider.createSymbolicLink(UnixFileSystemProvider.java:458)
    at java.base/java.nio.file.Files.createSymbolicLink(Files.java:1058)
    at copyapp.file.CopySymbolicLink.copy(CopySymbolicLink.java:24)
    at copyapp.model.CopyAppModel.copyFile(CopyAppModel.java:68)
    at copyapp.instanciation.SwingApp.createController(SwingApp.java:116)
    at copyapp.instanciation.SwingApp.<init>(SwingApp.java:30)
    at copyapp.instanciation.SwingAppFactory.createApplication(SwingAppFactory.java:8)
    at copyapp.client.mycp.main(mycp.java:29)