集合中的多列求和

前言

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

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);
    }
}

注解

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

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;
    }
}