public CRLNumberExtension(int crlNum) throws IOException {
  this(PKIXExtensions.CRLNumber_Id,false,BigInteger.valueOf(crlNum),NAME,LABEL);
}

public CRLNumberExtension ( int crlNum ) throws IOException { this ( PKIXExtensions . CRLNumber_Id , false , BigInteger . valueOf ( crlNum ) , NAME , LABEL ) ; }
create a crlnumberextension with the integer value . the criticality is set to false .
