docs: public boolean isValid() {
          if (TraceComponent.isAnyTracingEnabled() && tc.isDebugEnabled())
              Tr.debug(tc, "Checking validity of token " + this.getClass().getName());
  
          if (token != null) {
              // return if this token is still valid
              long currentTime = System.currentTimeMillis();
              long expiration = getExpiration();
              long timeleft = expiration - currentTime;
  
              if (TraceComponent.isAnyTracingEnabled() && tc.isDebugEnabled())
                  Tr.debug(tc, "Time left for token: " + timeleft);
  
              if (timeleft > 0) {
                  if (TraceComponent.isAnyTracingEnabled() && tc.isDebugEnabled())
                      Tr.debug(tc, "token is valid.");
                  return true;
              } else {
                  if (TraceComponent.isAnyTracingEnabled() && tc.isDebugEnabled())
                      Tr.debug(tc, "token is invalid.");
                  return false;
              }
          } else {
              if (TraceComponent.isAnyTracingEnabled() && tc.isDebugEnabled())
                  Tr.debug(tc, "token is null, returning invalid.");
              return false;
          }
      }