code: public void loadSimple(){
  		String pdbId = "4hhb";
  
  		AtomCache cache = new AtomCache();
  		cache.setUseMmCif(true);
  
  		StructureIO.setAtomCache(cache);
  
  		try {
  			Structure s = StructureIO.getStructure(pdbId);
  
  			System.out.println(pdbId + " has nr atoms: " + StructureTools.getNrAtoms(s));
  
  		} catch (Exception e){
  			e.printStackTrace();
  		}
  	}
docs: A basic example how to load an mmCif file and get a Structure object