code: public static FieldDeclaration mergeField(FieldDeclaration one, FieldDeclaration two) {
  
          if (isAllNull(one, two)) return null;
  
          FieldDeclaration fd = null;
  
          if (isAllNotNull(one, two)) {
  
              fd = new FieldDeclaration();
              fd.setType(mergeSelective(one.getType(), two.getType()));
              fd.setComment(mergeSelective(one.getComment(), two.getComment()));
              fd.setAnnotations(mergeListNoDuplicate(one.getAnnotations(), two.getAnnotations()));
              fd.setModifiers(mergeModifiers(one.getModifiers(), two.getModifiers()));
              fd.setJavaDoc(mergeSelective(one.getJavaDoc(), two.getJavaDoc()));
              fd.setVariables(mergeListNoDuplicate(one.getVariables(), two.getVariables()));
  
              LOG.info("merge FieldDeclaration --> {}", fd.getVariables());
  
          } else {
              fd = findFirstNotNull(one, two);
              LOG.info("add FieldDeclaration --> {}", fd.getVariables());
          }
          return fd;
      }
docs: /*
  合并字段声明