docs: protected ValueSet readAndDeleteInvalidationFile() {
          final String methodName = "readAndDeleteInvalidationFile()";
          final File f = new File(invalidationFileName);
          final CacheOnDisk cod = this;
          this.valueSet = new ValueSet(1);
          if (f.exists()) {
              AccessController.doPrivileged(new PrivilegedAction() {
                  public Object run() {
                      FileInputStream fis = null;
                      ObjectInputStream ois = null;
                      try {
                          fis = new FileInputStream(f);
                          ois = new ObjectInputStream(fis);
                          int size = ois.readInt();
                          cod.valueSet = new ValueSet(size);
                          for (int i = 0; i < size; i++) {
                              cod.valueSet.add(ois.readObject());
                          }
                      } catch (Throwable t1) {
                          com.ibm.ws.ffdc.FFDCFilter.processException(t1, "com.ibm.ws.cache.CacheOnDisk.readAndDeleteInvalidationFile", "1056", cod);
                          traceDebug(methodName, "cacheName=" + cod.cacheName + "\nException: " + ExceptionUtility.getStackTrace(t1));
                      } finally {
                          try {
                              if (ois != null) {
                                  ois.close();
                              }
                              if (fis != null) {
                                  fis.close();
                              }
                              f.delete();
                          } catch (Throwable t2) {
                              com.ibm.ws.ffdc.FFDCFilter
                                              .processException(t2, "com.ibm.ws.cache.CacheOnDisk.readAndDeleteInvalidationFile", "1068", cod);
                              traceDebug(methodName, "cacheName=" + cod.cacheName + "\nException: " + ExceptionUtility.getStackTrace(t2));
                          }
                      }
                      return null;
                  }
              });
          }
          traceDebug(methodName, "cacheName=" + this.cacheName + " " + invalidationFileName + " valueSet=" + valueSet.size());
          return this.valueSet;
      }