com.feilong.core.util

Class AggregateUtil

java.lang.Object

com.feilong.core.util.AggregateUtil

public final class AggregateUtil
extends Object

专门用来统计数据的工具类.

类似于sql里面的 统计函数 (Aggregate functions)

Since:

1.8.0

Author:

feilong

See Also:

"java.util.stream.Collectors"

Method Summary

Methods

Modifier and Type	Method and Description
static <O> Map<String,BigDecimal>	avg(Iterable<O> beanIterable, String[] propertyNames, int scale) 算术平均值.
static <O> BigDecimal	avg(Iterable<O> beanIterable, String propertyName, int scale) 算术平均值.
static <O> Map<String,Map<Object,Integer>>	groupCount(Iterable<O> beanIterable, String... propertyNames) 循环 beanIterable,只选择符合 includePredicate的对象,统计 propertyName的值出现的次数.
static <O,T> Map<T,Integer>	groupCount(Iterable<O> beanIterable, String propertyName) 循环 beanIterable,统计 propertyName 的值出现的次数.
static <O> Map<String,Map<Object,Integer>>	groupCount(Iterable<O> beanIterable, String[] propertyNames, Map<String,Transformer<Object,Object>> propertyValueAndTransformerMap) 循环 beanIterable,分别统计 propertyNames的值出现的次数,统计的时候支持使用 propertyValueAndTransformerMap 属性值的转换.
static <O> Map<String,Map<Object,Integer>>	groupCount(Iterable<O> beanIterable, String[] propertyNames, Map<String,Transformer<Object,Object>> propertyValueAndTransformerMap, Predicate<O> includePredicate) 循环 beanIterable,只选择符合 includePredicate的对象,分别统计 propertyNames的值出现的次数,统计的时候支持使用 propertyValueAndTransformerMap 属性值的转换.
static <O> Map<String,Map<Object,Integer>>	groupCount(Iterable<O> beanIterable, String[] propertyNames, Predicate<O> includePredicate) 循环 beanIterable,只选择符合 includePredicate的对象,分别统计 propertyNames的值出现的次数.
static <O,T> Map<T,Integer>	groupCount(Iterable<O> beanIterable, String propertyName, Predicate<O> includePredicate) 循环 beanIterable,只选择符合 includePredicate的对象,统计 propertyName的值出现的次数.
static <O,T> Map<T,BigDecimal>	groupSum(Iterable<O> beanIterable, String keyPropertyName, String sumPropertyName) 迭代beanIterable,取元素 keyPropertyName 的值为 key ,累计 sumPropertyName 属性值 为 value,返回 map.
static <O,T> Map<T,BigDecimal>	groupSum(Iterable<O> beanIterable, String keyPropertyName, String sumPropertyName, Predicate<O> includePredicate) 迭代beanIterable,提取符合 includePredicate的元素,取元素 keyPropertyName 的值为 key ,累计 sumPropertyName 属性值 为 value,返回 map.
static <O> Map<String,BigDecimal>	sum(Iterable<O> beanIterable, String... propertyNames) 总和,计算集合对象beanIterable 内指定的属性名 propertyNames 值的总和.
static <O> BigDecimal	sum(Iterable<O> beanIterable, String propertyName) 总和,计算集合对象beanIterable 内指定的属性名 propertyName 值的总和.
static <O> Map<String,BigDecimal>	sum(Iterable<O> beanIterable, String[] propertyNames, Predicate<O> includePredicate) 迭代beanIterable,提取符合 includePredicate的元素的指定 propertyNames 元素的值 ,累计总和.
static <O> BigDecimal	sum(Iterable<O> beanIterable, String propertyName, Predicate<O> includePredicate) 迭代beanIterable,提取 符合 includePredicate的元素的指定 propertyName 元素的值 ,累计总和.

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Method Detail

avg

public static <O> BigDecimal avg(Iterable<O> beanIterable,
                 String propertyName,
                 int scale)

算术平均值.

示例:

场景: 求的User list 里面 id属性 的平均值

 List<User> list = new ArrayList<>();
 list.add(new User(2L));
 list.add(new User(5L));
 list.add(new User(5L));
 AggregateUtil.avg(list, "id", 2)
 

返回: 4.00

Type Parameters:

O - the generic type

Parameters:

beanIterable - bean Iterable,诸如List<User>,Set<User>等

propertyName - 泛型O对象指定的属性名称,Possibly indexed and/or nested name of the property to be modified,参见 propertyName

scale - 标度,小数的位数,四舍五入,用于 BigDecimal.setScale(int, RoundingMode)
如果为零或正数,则标度是小数点后的位数。
如果为负数,则将该数的非标度值乘以 10 的负 scale 次幂 (通常情况用不到负数的情况)

Returns:

如果 beanIterable 是null或者empty,返回 null
如果 propertyName 是null,抛出 NullPointerException
如果 propertyName 是blank,抛出 IllegalArgumentException

See Also:

sum(Iterable, String...)

avg

public static <O> Map<String,BigDecimal> avg(Iterable<O> beanIterable,
                             String[] propertyNames,
                             int scale)

算术平均值.

说明:

1. 返回的 LinkedHashMap,key是 propertyNames的元素,value是基于这个属性名称获得的值的平均值;key的顺序是依照 propertyNames元素的顺序

示例:

场景: 求的User list 里面 age 以及id属性 的平均值

 User user1 = new User(2L);
 user1.setAge(18);
 
 User user2 = new User(3L);
 user2.setAge(30);
 
 List<User> list = toList(user1, user2);
 Map<String, BigDecimal> map = AggregateUtil.avg(list, ConvertUtil.toArray("id", "age"), 2);
 LOGGER.info(JsonUtil.format(map));
 

返回:

 {
 "id": 2.5,
 "age": 24
 }
 

Type Parameters:

O - the generic type

Parameters:

beanIterable - bean Iterable,诸如List<User>,Set<User>等

propertyNames - 泛型O对象指定的属性名称,Possibly indexed and/or nested name of the property to be modified,参见 propertyName

scale - 标度,小数的位数,四舍五入,用于 BigDecimal.setScale(int, RoundingMode)
如果为零或正数,则标度是小数点后的位数。
如果为负数,则将该数的非标度值乘以 10 的负 scale 次幂 (通常情况用不到负数的情况)

Returns:

如果 beanIterable 是null或者empty,返回 Collections.emptyMap()
如果propertyNames 是null 抛出 NullPointerException 异常
如果propertyNames 有元素是null 抛出 IllegalArgumentException

See Also:

sum(Iterable, String...)

sum

public static <O> BigDecimal sum(Iterable<O> beanIterable,
                 String propertyName)

总和,计算集合对象beanIterable 内指定的属性名 propertyName 值的总和.

说明:

1. 如果通过反射某个元素值是null,则使用默认值0代替,再进行累加

示例:

 List<User> list = new ArrayList<>();
 list.add(new User(2L));
 list.add(new User(5L));
 list.add(new User(5L));
 
 LOGGER.info("" + AggregateUtil.sum(list, "id"));
 

返回: 12

说明:

当你需要写这样的代码的时候,

 
 protected Integer getCookieShoppingCartLinesQty(List<CookieShoppingCartLine> cartLineList){
     Integer qty = 0;
     //获取cookie中的购物车行集合
     if (null != cartLineList && cartLineList.size() > 0){
         for (Iterator iterator = cartLineList.iterator(); iterator.hasNext();){
             CookieShoppingCartLine cookieShoppingCartLine = (CookieShoppingCartLine) iterator.next();
             qty += cookieShoppingCartLine.getQuantity();
         }
     }
     return qty;
 }
 

你可以写成:

 
 protected Integer getCookieShoppingCartLinesQty(List<CookieShoppingCartLine> cartLineList){
     return isNullOrEmpty(cartLineList) ? 0 : AggregateUtil.sum(cartLineList, "quantity").intValue();
 }
 

Type Parameters:

O - the generic type

Parameters:

beanIterable - bean Iterable,诸如List<User>,Set<User>等

propertyName - 泛型O对象指定的属性名称,Possibly indexed and/or nested name of the property to be modified,参见 propertyName

Returns:

如果 beanIterable 是null或者 empty,返回 null
如果 propertyName 是null,抛出 NullPointerException
如果 propertyName 是blank,抛出 IllegalArgumentException

See Also:

sum(Iterable, String...)

sum

public static <O> BigDecimal sum(Iterable<O> beanIterable,
                 String propertyName,
                 Predicate<O> includePredicate)

迭代beanIterable,提取 符合 includePredicate的元素的指定 propertyName 元素的值 ,累计总和.

说明:

1. 如果通过反射某个元素值是null,则使用默认值0代替,再进行累加

示例:

场景: 统计user list(条件是 id >10),id属性值的总和

 
 List<User> list = new ArrayList<>();
 list.add(new User(2L));
 list.add(new User(50L));
 list.add(new User(50L));
 
 AggregateUtil.sum(list, "id", new Predicate<User>(){
 
     @Override
     public boolean evaluate(User user){
         return user.getId() > 10L;
     }
 });
 
 

返回: new BigDecimal(100L)

当然这段代码,你还可以优化成:

 Predicate<Long> predicate = new ComparatorPredicate<Long>(10L, ComparatorUtils.<Long> naturalComparator(), Criterion.LESS);
 BigDecimal sum = AggregateUtil.sum(list, "id", new BeanPredicate<User>("id", predicate));
 

Type Parameters:

O - the generic type

Parameters:

beanIterable - bean Iterable,诸如List<User>,Set<User>等

propertyName - 泛型O对象指定的属性名称,Possibly indexed and/or nested name of the property to be modified,参见 propertyName

includePredicate - the include predicate

Returns:

如果 beanIterable 是null或者 empty,返回 null
如果 propertyName 是null,抛出 NullPointerException
如果 propertyName 是blank,抛出 IllegalArgumentException
如果 includePredicate 是null,那么迭代所有的元素
如果beanIterable没有符合 includePredicate的元素,返回 null

See Also:

sum(Iterable, String[], Predicate)

sum

public static <O> Map<String,BigDecimal> sum(Iterable<O> beanIterable,
                             String... propertyNames)

总和,计算集合对象beanIterable 内指定的属性名 propertyNames 值的总和.

说明:

1. 如果通过反射某个元素值是null,则使用默认值0代替,再进行累加

示例:

场景: 在user list 中,分别统计 id属性以及age属性值总和

 User user1 = new User(2L);
 user1.setAge(18);
 
 User user2 = new User(3L);
 user2.setAge(30);
 
 Map<String, BigDecimal> map = AggregateUtil.sum(toList(user1, user2), "id", "age");
 LOGGER.info(JsonUtil.format(map));
 

返回:

 {
 "id": 5,
 "age": 48
 }
 

Type Parameters:

O - the generic type

Parameters:

beanIterable - bean Iterable,诸如List<User>,Set<User>等

propertyNames - 泛型O对象指定的属性名称,Possibly indexed and/or nested name of the property to be modified,参见 propertyName

Returns:

如果 beanIterable 是null或者empty,返回 Collections.emptyMap()
如果propertyNames 是null 抛出 NullPointerException 异常
如果propertyNames 有元素是null 抛出 IllegalArgumentException

See Also:

sum(Iterable, String[], Predicate)

sum

public static <O> Map<String,BigDecimal> sum(Iterable<O> beanIterable,
                             String[] propertyNames,
                             Predicate<O> includePredicate)

迭代beanIterable,提取符合 includePredicate的元素的指定 propertyNames 元素的值 ,累计总和.

示例:

 User user1 = new User(10L);
 user1.setName("刘备");
 user1.setAge(50);
 
 User user2 = new User(20L);
 user1.setName("关羽");
 user2.setAge(50);
 
 User user3 = new User(100L);
 user3.setName("张飞");
 user3.setAge(100);
 
 List<User> list = toList(user1, user2, user3);
 Map<String, BigDecimal> map = AggregateUtil.sum(list, ConvertUtil.toArray("id", "age"), new Predicate<User>(){
 
     @Override
     public boolean evaluate(User user){
         return !"张飞".equals(user.getName());
     }
 });
 LOGGER.debug(JsonUtil.format(map));
 
 

返回:

 {
 "id": 30,
 "age": 100
 }
 

Type Parameters:

O - the generic type

Parameters:

beanIterable - bean Iterable,诸如List<User>,Set<User>等

propertyNames - 泛型O对象指定的属性名称,Possibly indexed and/or nested name of the property to be modified,参见 propertyName

includePredicate - the include predicate

Returns:

如果 beanIterable 是null或者empty,返回 Collections.emptyMap()
如果通过反射某个元素值是null,则使用默认值0代替,再进行累加
如果 includePredicate 是null,那么迭代所有的元素
如果beanIterable没有符合 includePredicate的元素,返回 new LinkedHashMap

Throws:

NullPointerException - 如果propertyNames 是null

IllegalArgumentException - 果propertyNames 有元素 是null

groupSum

public static <O,T> Map<T,BigDecimal> groupSum(Iterable<O> beanIterable,
                               String keyPropertyName,
                               String sumPropertyName)

迭代beanIterable,取元素 keyPropertyName 的值为 key ,累计 sumPropertyName 属性值 为 value,返回 map.

示例:

统计 user list 按照姓名分组, 累加每个人的 age 总和

 List<User> list = toList(//
                 new User("张飞", 20),
                 new User("关羽", 20),
                 new User("刘备", 20),
                 new User("刘备", 20));
 
 Map<String, BigDecimal> map = AggregateUtil.groupSum(list, "name", "age");
 
 

assertThat:

 assertThat(
                 map,
                 allOf(//
                                 hasEntry("刘备", toBigDecimal(40)),
                                 hasEntry("张飞", toBigDecimal(20)),
                                 hasEntry("关羽", toBigDecimal(20))));
 

Type Parameters:

O - the generic type

Parameters:

beanIterable - bean Iterable,诸如List<User>,Set<User>等

keyPropertyName - 泛型O对象指定的属性名称,Possibly indexed and/or nested name of the property to be modified,参见 propertyName

sumPropertyName - 泛型O对象指定的属性名称,Possibly indexed and/or nested name of the property to be modified,参见 propertyName

Returns:

如果 beanIterable 是null或者empty,返回 Collections.emptyMap()
如果通过反射某个元素值是null,则使用默认值0代替,再进行累加
如果 keyPropertyName 是null,抛出 NullPointerException
如果 keyPropertyName 是blank,抛出 IllegalArgumentException
如果 sumPropertyName 是null,抛出 NullPointerException
如果 sumPropertyName 是blank,抛出 IllegalArgumentException

Since:

1.13.2

groupSum

public static <O,T> Map<T,BigDecimal> groupSum(Iterable<O> beanIterable,
                               String keyPropertyName,
                               String sumPropertyName,
                               Predicate<O> includePredicate)

迭代beanIterable,提取符合 includePredicate的元素,取元素 keyPropertyName 的值为 key ,累计 sumPropertyName 属性值 为 value,返回 map.

统计 user list 所有 age 小于等于30的, 按照姓名分组, 累加每个人的 age 总和

 
 Predicate<User> comparatorPredicate = BeanPredicateUtil.comparatorPredicate("age", 30, Criterion.GREATER_OR_EQUAL);
 
 List<User> list = toList(//
                 new User("张飞", 20),
                 new User("关羽", 20),
                 new User("刘备", 20),
                 new User("刘备", 50),
                 new User("刘备", 20));
 
 Map<String, BigDecimal> map = AggregateUtil.groupSum(list, "name", "age",comparatorPredicate);
 
 

assertThat:

 assertThat(
                 map,
                 allOf(//
                                 hasEntry("刘备", toBigDecimal(40)),
                                 hasEntry("张飞", toBigDecimal(20)),
                                 hasEntry("关羽", toBigDecimal(20))));
 

Type Parameters:

O - the generic type

T - the generic type

Parameters:

beanIterable - bean Iterable,诸如List<User>,Set<User>等

keyPropertyName - 泛型O对象指定的属性名称,Possibly indexed and/or nested name of the property to be modified,参见 propertyName

sumPropertyName - 泛型O对象指定的属性名称,Possibly indexed and/or nested name of the property to be modified,参见 propertyName

includePredicate - the include predicate

Returns:

如果 beanIterable 是null或者empty,返回 Collections.emptyMap()
如果通过反射某个元素值是null,则使用默认值0代替,再进行累加
如果 includePredicate 是null,那么迭代所有的元素
如果 beanIterable没有符合 includePredicate的元素,返回 new LinkedHashMap 如果 keyPropertyName 是null,抛出 NullPointerException
如果 keyPropertyName 是blank,抛出 IllegalArgumentException
如果 sumPropertyName 是null,抛出 NullPointerException
如果 sumPropertyName 是blank,抛出 IllegalArgumentException

Since:

1.13.2

groupCount

public static <O,T> Map<T,Integer> groupCount(Iterable<O> beanIterable,
                              String propertyName)

循环 beanIterable,统计 propertyName 的值出现的次数.

说明:

1. 返回的LinkedHashMap,key是propertyName对应的值,value是该值出现的次数;
   顺序是 beanIterable propertyName的值的顺序

示例:

场景: 统计user list,属性名字是name 的值的数量

 List<User> list = new ArrayList<>();
 list.add(new User("张飞"));
 list.add(new User("关羽"));
 list.add(new User("刘备"));
 list.add(new User("刘备"));
 
 Map<String, Integer> map = AggregateUtil.groupCount(list, "name");
 LOGGER.info(JsonUtil.format(map));
 

返回:

 {
 "张飞": 1,
 "关羽": 1,
 "刘备": 2
 }
 

Type Parameters:

O - the generic type

T - the generic type

Parameters:

beanIterable - bean Iterable,诸如List<User>,Set<User>等

propertyName - 泛型O对象指定的属性名称,Possibly indexed and/or nested name of the property to be modified,参见 propertyName

Returns:

如果 beanIterable 是null或者empty,返回 Collections.emptyMap()
如果 propertyName 是null,抛出 NullPointerException
如果 propertyName 是blank,抛出 IllegalArgumentException

See Also:

groupCount(Iterable , String, Predicate), CollectionUtils.getCardinalityMap(Iterable)

groupCount

public static <O,T> Map<T,Integer> groupCount(Iterable<O> beanIterable,
                              String propertyName,
                              Predicate<O> includePredicate)

循环 beanIterable,只选择符合 includePredicate的对象,统计 propertyName的值出现的次数.

说明:

1. 返回的LinkedHashMap,key是propertyName对应的值,value是该值出现的次数;
   顺序是 beanIterable propertyName的值的顺序

示例:

场景: 统计user list(条件是 age > 30 的user),name属性值的数量

 List<User> list = new ArrayList<>();
 list.add(new User("张飞", 20));
 list.add(new User("关羽", 30));
 list.add(new User("刘备", 40));
 list.add(new User("赵云", 50));
 
 Map<String, Integer> map = AggregateUtil.groupCount(list, "name", new Predicate<User>(){
     @Override
     public boolean evaluate(User user){
         return user.getAge() > 30;
     }
 });
 LOGGER.debug(JsonUtil.format(map));
 
 

返回:

 {
 "刘备": 1,
 "赵云": 1
 }
 
 

Type Parameters:

O - the generic type

T - the generic type

Parameters:

beanIterable - bean Iterable,诸如List<User>,Set<User>等

propertyName - 泛型O对象指定的属性名称,Possibly indexed and/or nested name of the property to be modified,参见 propertyName

includePredicate - 只选择 符合 includePredicate的对象,如果是null 则统计集合中全部的元素

Returns:

如果 beanIterable 是null或者empty,返回 Collections.emptyMap()
如果 propertyName 是null,抛出 NullPointerException
如果 propertyName 是blank,抛出 IllegalArgumentException
如果 includePredicate 是null,则统计集合中全部的元素

See Also:

CollectionUtils.getCardinalityMap(Iterable)

groupCount

public static <O> Map<String,Map<Object,Integer>> groupCount(Iterable<O> beanIterable,
                                             String... propertyNames)

循环 beanIterable,只选择符合 includePredicate的对象,统计 propertyName的值出现的次数.

说明:

1. 返回的LinkedHashMap,key是propertyName名字,子map的key是propertyName对应的值,value是该值出现的次数;
   顺序是 beanIterable propertyName的值的顺序

示例:

场景: 统计user list,属性名字是name 的值的数量 以及age值的数量

 List<User> list = toList(//
                 new User("张飞", 20),
                 new User("关羽", 30),
                 new User("赵云", 50),
                 new User("刘备", 40),
                 new User("刘备", 30),
                 new User("赵云", 50));
 
 Map<String, Map<Object, Integer>> map = AggregateUtil.groupCount(list, toArray("name", "age"));
 
 LOGGER.debug(JsonUtil.format(map));
 

返回:

     {
         "age":         {
             "20": 1,
             "30": 2,
             "50": 2,
             "40": 1
         },
         "name":         {
             "张飞": 1,
             "关羽": 1,
             "赵云": 2,
             "刘备": 2
         }
     }
 
 

Type Parameters:

O - the generic type

Parameters:

beanIterable - bean Iterable,诸如List<User>,Set<User>等

propertyNames - 泛型O对象指定的属性名称,Possibly indexed and/or nested name of the property to be modified,参见 propertyName

Returns:

如果 beanIterable 是null或者empty,返回 Collections.emptyMap()
如果 propertyNames 是null,抛出 NullPointerException
如果 propertyNames 是empty,抛出 IllegalArgumentException
如果 循环的propertyName 是null,抛出 NullPointerException
如果 循环的propertyName 是empty或者blank,抛出 IllegalArgumentException

Since:

1.10.6, 1.10.7 change param type from String[] propertyNames to String...propertyNames
change return type from Map<String, Map<T, Integer>> to Map<String, Map<Object, Integer>>

See Also:

CollectionUtils.getCardinalityMap(Iterable)

groupCount

public static <O> Map<String,Map<Object,Integer>> groupCount(Iterable<O> beanIterable,
                                             String[] propertyNames,
                                             Predicate<O> includePredicate)

循环 beanIterable,只选择符合 includePredicate的对象,分别统计 propertyNames的值出现的次数.

说明:

1. 返回的LinkedHashMap,key是propertyName名字,子map的key是propertyName对应的值,value是该值出现的次数;
   顺序是 beanIterable propertyName的值的顺序

示例:

场景: 统计user list(条件是 age > 30 的user),name属性值的数量以及age 的数量

 List<User> list = toList(//
                 new User("张飞", 20),
                 new User("关羽", 30),
                 new User("赵云", 50),
                 new User("刘备", 40),
                 new User("刘备", 30),
                 new User("赵云", 50));
 
 Predicate<User> comparatorPredicate = BeanPredicateUtil.comparatorPredicate("age", 30, Criterion.LESS);
 Map<String, Map<Object, Integer>> map = AggregateUtil.groupCount(list, toArray("name", "age"), comparatorPredicate);
 
 LOGGER.debug(JsonUtil.format(map));
 

返回:

     {
         "age":         {
             "50": 2,
             "40": 1
         },
         "name":         {
             "赵云": 2,
             "刘备": 1
         }
     }
 

Type Parameters:

O - the generic type

Parameters:

beanIterable - bean Iterable,诸如List<User>,Set<User>等

propertyNames - 泛型O对象指定的属性名称,Possibly indexed and/or nested name of the property to be modified,参见 propertyName

includePredicate - 只选择 符合 includePredicate的对象,如果是null 则统计集合中全部的元素

Returns:

如果 beanIterable 是null或者empty,返回 Collections.emptyMap()
如果 propertyNames 是null,抛出 NullPointerException
如果 propertyNames 是empty,抛出 IllegalArgumentException
如果 循环的propertyName 是null,抛出 NullPointerException
如果 循环的propertyName 是empty或者blank,抛出 IllegalArgumentException
如果 includePredicate 是null,则统计集合中全部的元素

Since:

1.10.6, 1.10.7 change return type from Map<String, Map<T, Integer>> to Map<String, Map<Object, Integer>>

See Also:

CollectionUtils.getCardinalityMap(Iterable)

groupCount

public static <O> Map<String,Map<Object,Integer>> groupCount(Iterable<O> beanIterable,
                                             String[] propertyNames,
                                             Map<String,Transformer<Object,Object>> propertyValueAndTransformerMap)

循环 beanIterable,分别统计 propertyNames的值出现的次数,统计的时候支持使用 propertyValueAndTransformerMap 属性值的转换.

说明:

1. 返回的LinkedHashMap,key是propertyName名字,子map的key是propertyName对应的值,value是该值出现的次数;
   顺序是 beanIterable propertyName的值的顺序

示例:

场景: 统计user list,name属性值的数量以及age 的数量,并且 age以范围区间统计

    List<User> list = toList(//
                        new User("张飞", 20),
                        new User("关羽", 30),
                        new User("刘备", 32),
                        new User("刘备", 40),
                        new User("赵云", 51),
                        new User("赵云", 50));

        Transformer<?, ?> transformer = new Transformer<Integer, String>(){

            public String transform(Integer input){
                if (input >= 50){
                    return ">=50";
                }
                if (input >= 30 && input < 50){
                    return ">=30&&<50";
                }
                if (input >= 20 && input < 30){
                    return ">=20&&<30";
                }               
                throw new UnsupportedOperationException("value not support!");
            }

        };

        //---------------------------------------------------------------
        Map<String, Transformer<Object, Object>> propertyValueAndTransformerMap = toMap("age", (Transformer<Object, Object>) transformer);

        //---------------------------------------------------------------

        Map<String, Map<Object, Integer>> map = AggregateUtil
                        .groupCount(list, toArray("name", "age"), propertyValueAndTransformerMap);

        LOGGER.debug(JsonUtil.format(map));
 

返回:

    {
        "name":         {
            "张飞": 1,
            "关羽": 1,
            "刘备": 2,
            "赵云": 2
        },
        "age":         {
            ">=20&&<30": 1,
            ">=30&&<50": 3,
            ">=50": 2
        }
    }
 

Type Parameters:

O - the generic type

Parameters:

beanIterable - bean Iterable,诸如List<User>,Set<User>等

propertyNames - 泛型O对象指定的属性名称,Possibly indexed and/or nested name of the property to be modified,参见 propertyName

propertyValueAndTransformerMap - the property name value converter map

Returns:

如果 propertyValueAndTransformerMap 是null或者empty,方法等于 groupCount(Iterable, String[], Predicate)
如果 beanIterable 是null或者empty,返回 Collections.emptyMap()
如果 propertyNames 是null,抛出 NullPointerException
如果 propertyNames 是empty,抛出 IllegalArgumentException
如果 循环的propertyName 是null,抛出 NullPointerException
如果 循环的propertyName 是empty或者blank,抛出 IllegalArgumentException

Since:

1.10.7

See Also:

CollectionUtils.getCardinalityMap(Iterable)

groupCount

public static <O> Map<String,Map<Object,Integer>> groupCount(Iterable<O> beanIterable,
                                             String[] propertyNames,
                                             Map<String,Transformer<Object,Object>> propertyValueAndTransformerMap,
                                             Predicate<O> includePredicate)

循环 beanIterable,只选择符合 includePredicate的对象,分别统计 propertyNames的值出现的次数,统计的时候支持使用 propertyValueAndTransformerMap 属性值的转换.

说明:

1. 返回的LinkedHashMap,key是propertyName名字,子map的key是propertyName对应的值,value是该值出现的次数;
   顺序是 beanIterable propertyName的值的顺序

示例:

场景: 统计user list(条件是 age > 30 的user),name属性值的数量以及age 的数量,并且 age以范围区间统计

    List<User> list = toList(//
                        new User("张飞", 20),
                        new User("关羽", 30),
                        new User("刘备", 32),
                        new User("刘备", 40),
                        new User("赵云", 51),
                        new User("赵云", 50));

        Transformer<?, ?> transformer = new Transformer<Integer, String>(){

            public String transform(Integer input){
                if (input >= 50){
                    return ">=50";
                }
                if (input >= 30 && input < 50){
                    return ">=30&&<50";
                }
                throw new UnsupportedOperationException("value not support!");
            }

        };

        //---------------------------------------------------------------
        Map<String, Transformer<Object, Object>> propertyValueAndTransformerMap = toMap("age", (Transformer<Object, Object>) transformer);

        Predicate<User> comparatorPredicate = BeanPredicateUtil.comparatorPredicate("age", 30, Criterion.LESS);

        //---------------------------------------------------------------

        Map<String, Map<Object, Integer>> map = AggregateUtil
                        .groupCount(list, toArray("name", "age"), propertyValueAndTransformerMap, comparatorPredicate);

        LOGGER.debug(JsonUtil.format(map));
 

返回:

    {
        "name":         {
            "刘备": 2,
            "赵云": 2
        },
        "age":         {
            ">=30&&<50": 2,
            ">=50": 2
        }
    }
 

Type Parameters:

O - the generic type

Parameters:

beanIterable - bean Iterable,诸如List<User>,Set<User>等

propertyNames - 泛型O对象指定的属性名称,Possibly indexed and/or nested name of the property to be modified,参见 propertyName

propertyValueAndTransformerMap - the property name value converter map

includePredicate - 只选择 符合 includePredicate的对象,如果是null 则统计集合中全部的元素

Returns:

如果 propertyValueAndTransformerMap 是null或者empty,方法等于 groupCount(Iterable, String[], Predicate)
如果 beanIterable 是null或者empty,返回 Collections.emptyMap()
如果 propertyNames 是null,抛出 NullPointerException
如果 propertyNames 是empty,抛出 IllegalArgumentException
如果 循环的propertyName 是null,抛出 NullPointerException
如果 循环的propertyName 是empty或者blank,抛出 IllegalArgumentException
如果 includePredicate 是null,则统计集合中全部的元素

Since:

1.10.7

See Also:

CollectionUtils.getCardinalityMap(Iterable)