code: @Override
      public void visitClassContext(ClassContext classContext) {
          if (cloneableClass == null) {
              return;
          }
  
          try {
              JavaClass cls = classContext.getJavaClass();
              if (cls.implementationOf(cloneableClass)) {
                  stack = new OpcodeStack();
                  super.visitClassContext(classContext);
              }
          } catch (ClassNotFoundException cnfe) {
              bugReporter.reportMissingClass(cnfe);
          } finally {
              stack = null;
          }
      }
docs: override the visitor to look for classes that implement Cloneable
  
  @param classContext
  the context object of the class to be checked