code: public static File getIndexFile(String filename) {
          String tmpDir = System.getProperty("java.io.tmpdir");
          File f = new File(filename);
          File indexFile = new File(tmpDir, f.getName() + "_cdk.index");
          f = null;
          return indexFile;
      }
docs: Opens the file index file <code>_cdk.index</code> in a temporary folder, as specified by "java.io.tmpdir" property.
  
  @param filename the name of the file for which the index was generated
  @return a file object representing the index file