集合中的多列求和

前言

1. 最近公司做项目需要对集合中的很多字段进行求和操作,很多是多少70多个吧.

代码实现

1. 求和工具类

   public class NumberUtil {
   
       public static <T extends Number> T add(List<T> numbs) {
           if (numbs == null || numbs.isEmpty()) {
               return null;
           }
           Class<? extends Number> aClass = numbs.get(0).getClass();
           if (isBaseTypePackaging(aClass) || aClass.isPrimitive()) {
               Integer sumInteger = 0;
               Long sumLong = 0L;
               BigDecimal bigDecimal = new BigDecimal("0.0");
               for (T numb : numbs) {
                   if (numb == null) {
                       continue;
                   }
                   if (aClass.isAssignableFrom(Integer.class)) {
                       sumInteger += numb.intValue();
                   } else if (aClass.isAssignableFrom(Long.class)) {
                       sumLong += numb.longValue();
                   }
               }
               if (aClass.isAssignableFrom(Integer.class)) {
                   return (T) sumInteger;
               } else if (aClass.isAssignableFrom(Long.class)) {
                   return (T) sumLong;
               }
               return null;
           } else if (aClass.isAssignableFrom(BigDecimal.class)) {
               BigDecimal count = new BigDecimal("0.00");
               for (T numb : numbs) {
                   if (numb == null) {
                       continue;
                   }
                   BigDecimal num = (BigDecimal) numb;
                   count = count.add(num);
               }
               return (T) count;
           }
           return null;
       }
   
       /**
        * 是否是基本类型的包装类
        *
        * @param c 对象class类型
        * @return boolean true 是 ,false 否
        */
       private static boolean isBaseTypePackaging(Class c) {
           return c.equals(java.lang.Integer.class) || c.equals(java.lang.Byte.class) || c.equals(java.lang.Long.class) || c.equals(java.lang.Double.class) || c.equals(java.lang.Float.class) || c.equals(java.lang.Character.class) || c.equals(java.lang.Short.class) || c.equals(java.lang.Boolean.class);
       }
   }
   

2. 注解

   @Target(ElementType.FIELD)
   @Retention(RetentionPolicy.RUNTIME)
   public @interface SumIgnore {
   }
   

3. 反射实现类

   public class SumUtilPro {
       private static final Set<String> calTypeSet = new HashSet<>(Arrays.asList("Integer","Long","BigDecimal"));
   
       public static <T, E extends Number> T mapperSum(List<T> list, Class<T> clazz) throws Exception {
           T obj = clazz.newInstance();
           Field[] declaredFields = clazz.getDeclaredFields();
           for (Field declaredField : declaredFields) {
               declaredField.setAccessible(true);
               SumIgnore sumIgnore = declaredField.getAnnotation(SumIgnore.class);
               if (sumIgnore != null) {
                   continue;
               }
               Class<?> filedType = declaredField.getType();
               String fileSampleName = filedType.getSimpleName();
               if (!calTypeSet.contains(fileSampleName)) {
                   continue;
               }
               String fieldName = firstLetterToUpper(declaredField.getName());
               Method method = clazz.getMethod("get" + fieldName);
               List<E> data = new ArrayList<>();
               for (T t : list) {
                   E e = (E) method.invoke(t);
                   if (ObjectUtil.isNotNull(e)) {
                       data.add(e);
                   }
               }
               if (ObjectUtil.isEmpty(data)) {
                   continue;
               }
               E add = NumberUtil.add(data);
               String setMethodName = "set" + fieldName;
               Method setMethod = clazz.getMethod(setMethodName, filedType);
               setMethod.invoke(obj, add);
           }
           return handleNull(obj);
   
       }
   
       private static String firstLetterToUpper(String str) {
           char[] array = str.toCharArray();
           array[0] -= 32;
           return String.valueOf(array);
       }
   
       public static <T> T handleNull(T o) throws Exception {
           Class<? extends Object> cls = o.getClass();
           Field[] fields = cls.getDeclaredFields();
           for (int i = 0; i < fields.length; i++) {
               Field f = fields[i];
               f.setAccessible(true);
               System.out.println("属性名：" + f.getName() + "；属性值：" + f.get(o) + "；字段类型：" + f.getType());
               if (f.get(o) == null) {
                   String fileTypeName = f.getType().getSimpleName();
                   switch (fileTypeName) {
                       case "String":
                           f.set(o, "");
                           break;
                       case "Long":
                           f.set(o, 0l);
                           break;
                       case "Integer":
                           f.set(o, 0);
                           break;
                       case "BigDecimal":
                           f.set(o, new BigDecimal("0.00"));
                           break;
                       default:
                           f.set(o, 0.00);
                           break;
                   }
               }
           }
           return o;
       }
   }