package org.ethereum.util;

import java.io.File;

public class FileUtil {

    public static boolean recursiveDelete(String fileName) {
        File file = new File(fileName);
        if (file.exists()) {
            //check if the file is a directory
            if (file.isDirectory()) {
                if ((file.list()).length > 0) {
                    for(String s:file.list()){
                        //call deletion of file individually
                        recursiveDelete(fileName + "\\" + s);
                    }
                }
            }

            file.setWritable(true);
            boolean result = file.delete();
            return result;
        } else {
            return false;
        }
    }

}

@@ -494,12 +494,44 @@
 e + 
-%22%5C%5C%22
+System.getProperty(%22file.separator%22)
  + s

Fix in FileUtil: \ replaced with file.separator from system properties; it guarantees correct behaviour under different platforms