File helper class

FileUtil.java

import java.io.File;
import java.io.FilenameFilter;
import java.util.HashSet;
import java.util.List;
import java.util.Set;

public class FileUtil {

   private static String getSimpleFileName(final String fileName){
      if(fileName == null || fileName.length() == 0)
         return fileName;
      final String[] arr = fileName.split(File.separator);
      return arr[arr.length - 1];
   }
   
   public static boolean deleteFilesExcept(List<String> fileNames, String folderName){
      File folder = new File(folderName);
      if(!folder.exists() || ! folder.isDirectory() || !folder.canWrite()) {
         throw new RuntimeException("Folder "+folderName+" is not accessible or is not a directory");
      }
      final Set<String> fNames = new HashSet<String>();
      for(String fileName : fileNames) {
         fNames.add(getSimpleFileName(fileName));         
      }
      final File[] filesToDelete = folder.listFiles(new FilenameFilter() {         
         @Override
         public boolean accept(File dir, String name) {
            return !fNames.contains(name);
         }
      });
      for(final File f : filesToDelete) {
         f.delete();
      }
      return true;
   }
   
}