visad/src/main/java/ucar/nc2/iosp/gempak/GempakGridServiceProvider.java
public boolean sync() throws IOException {
    if ((gemreader.getInitFileSize() < raf.length()) && extendIndex) {
      gemreader.init(true);
      GridIndex index = gemreader.getGridIndex();
      // reconstruct the ncfile objects
      ncfile.empty();
      open(index, null);
      return true;
    }
    return false;
  }
public boolean sync() throws IOException {
    if ((gemreader.getInitFileSize() < raf.length()) && extendIndex) {
      gemreader.init(true);
      GridIndex index = gemreader.getGridIndex();
      // reconstruct the ncfile objects
      ncfile.empty();
      open(index, null);
      return true;
    }
    return false;
  }
Sync the file

@return true if needed to sync
@throws IOException problem synching the file