public void addSourceType(final CertificateSourceType certSourceType){
  if (certSourceType != null) {
    sources.add(certSourceType);
  }
}

public void addSourceType ( final CertificateSourceType certSourceType ) { if ( certSourceType != null ) { sources . add ( certSourceType ) ; } }
this method adds the source type of the certificate ( what is its origin ) . each source is present only once .
