code: @Override
      public ValidationReport validateBond(IBond subject) {
          ValidationReport report = new ValidationReport();
          // only consider two atom bonds
          if (subject.getAtomCount() == 2) {
              double distance = subject.getBegin().getPoint3d().distance(subject.getEnd().getPoint3d());
              if (distance > 3.0) { // should really depend on the elements
                  ValidationTest badBondLengthError = new ValidationTest(subject,
                          "Bond length cannot exceed 3 Angstroms.",
                          "A bond length typically is between 0.5 and 3.0 Angstroms.");
                  report.addError(badBondLengthError);
              }
          }
          return report;
      }
docs: assumes 1 unit in the coordinate system is one angstrom