code: public static Map<String,String> getSystemConfiguration()
      {
          if(LibraryConfigurationLoader.systemConfiguration==null)
          {
              synchronized(LibraryConfigurationLoader.class)
              {
                  if(LibraryConfigurationLoader.systemConfiguration==null)
                  {
                      //read properties
                      Properties properties=LibraryConfigurationLoader.readInternalAndExternalConfiguration();
  
                      //convert to map
                      Map<String,String> map=new HashMap<String,String>(properties.size());
                      SpiUtil.copyPropertiesToMap(properties,map);
  
                      //normalize map
                      map=new HashMap<String,String>(map);
                      
                      //prevent changes
                      map=Collections.unmodifiableMap(map);
  
                      //set instance
                      LibraryConfigurationLoader.systemConfiguration=map;
                  }
              }
          }
          
          return LibraryConfigurationLoader.systemConfiguration;
      }
docs: This function returns the system configuration (internal and external
  fax4j.properties files).
  
  @return  The system configuration