code: @Override
      public void flush() throws IOException {
  
          if (_callback != null) {
              if (!this._isReady) {
                  if (TraceComponent.isAnyTracingEnabled() && tc.isDebugEnabled()) {
                      Tr.debug(tc, "Cannot flush stream , output not ready: " + this);
                  }
                  return;
              }
              else {
                  validate();
                  flushBuffers();
              }
          }
          else {
              super.flush();
          }
  
      }
docs: /*
  @see java.io.OutputStream#flush()