code: public static IChemObjectBuilder getInstance() {
          IChemObjectBuilder result = instance;
          if (result == null) {
              result = instance;
              synchronized (LOCK) {
                  if (result == null) {
                      instance = result = new DefaultChemObjectBuilder();
                  }
              }
          }
          return result;
      }
docs: Access the singleton instance of this DefaultChemObjectBuilder.
  <pre>{@code
  
  // get the builder instance
  IChemObjectBuilder builder = DefaultChemObjectBuilder.getInstance();
  
  // using the builder...
  // create an IAtom using the default constructor
  IAtom atom = builder.newInstance(IAtom.class);
  
  // create a carbon atom
  IAtom c1 = builder.newInstance(IAtom.class, "C");
  }</pre>
  
  @return a DefaultChemObjectBuilder instance