code: public static Field generateField(String fieldName, JavaVisibility visibility, FullyQualifiedJavaType javaType, String initString) {
          Field field = new Field(fieldName, javaType);
          field.setVisibility(visibility);
          if (initString != null) {
              field.setInitializationString(initString);
          }
          return field;
      }
docs: 生成属性
  @param fieldName  常量名称
  @param visibility 可见性
  @param javaType   类型
  @param initString 初始化字段
  @return