If else imbriqué qui ressort toujours un resultat nul

        this.commande = this.getCommand();

 public String getCommand(){
  String commande =null;
  String UpOrDownLink = null;
  String LogicalChannel = null;
  String TransportChannel = null;
  if (this.isType("MU")){
    UpOrDownLink = this.getField(24);
    LogicalChannel = this.getField(25);
    TransportChannel = this.getField(26);
    if (UpOrDownLink == "D" & LogicalChannel == "DC" ) {
     commande = "DL-DCCH-Message ";
   }else if (UpOrDownLink == "U" & LogicalChannel == "DC" ) {
     commande = "UL-DCCH-Message ";
   }else if (UpOrDownLink == "D" & LogicalChannel == "CC" ) {
     commande = "DL-CCCH-Message ";
   }else if (UpOrDownLink == "U" & LogicalChannel == "CC" ) {
     commande = "UL-CCCH-Message ";
   }else if ( LogicalChannel == "PC" ) {
     commande = "PCCH-Message ";
   }else if ( LogicalChannel == "BC" & TransportChannel == "FA" ) {
     commande = "BCCH-FACH-Message ";
   }else if ( LogicalChannel == "BC" & TransportChannel == "B" ) {
     commande = "BCCH-BCH-Message ";
   }
  }

  return commande;
 }