com.feilong.core.util

Class CollectionsUtil

java.lang.Object

com.feilong.core.util.CollectionsUtil

public final class CollectionsUtil
extends Object

Collection 工具类,是 Collections 的扩展和补充.

Collections Framework关系图:

关于 Collection:

字段	说明
Collection	一组对象的集合,一般不直接使用 有 add,size,clear, contains ,remove,removeAll ,retainAll, toArray方法 没有get()方法.只能通过iterator()遍历元素

关于 List:

interface/class	说明
List	An ordered collection integer index for insert and search. 除了继承Collection接口方法外,有自己的方法定义: get(int) indexOf lastIndexOf listIterator set(int) subList(int,int) optional:可空,可重复
ArrayList	Resizable-array implementation of the List interface 元素可空 有自己控制容量(数组大小)的方法 扩容: see ArrayList.ensureCapacity(int), 在jdk1.6里面,int newCapacity = (oldCapacity * 3)/2 + 1 通常是1.5倍 在jdk1.7+里面,代码进行了优化
LinkedList	Linked list implementation,双向链表 元素可空
Vector	growable array of objects 线程安全的动态数组 synchronized 操作基本和ArrayList相同
Stack	last-in-first-out (LIFO) stack of objects

关于 Set:

interface/class	说明
Set	A collection contains no duplicate elements Set和Collection拥有一模一样的接口名称
HashSet	backed by a HashMap instance. makes no guarantees as to the iteration order of the set; 不保证顺序 permits the null element.允许空元素
LinkedHashSet	Hash Map and linked list implementation of the Set interface, with predictable iteration order
TreeSet	A NavigableSet implementation based on a TreeMap. ordered using their natural ordering, or by a Comparator provided at set creation time
EnumSet	A specialized Set implementation for use with enum types. Null elements are not permitted. natural order (the order in which the enum constants are declared. abstract class. 以位向量的形式存储,这种存储形式非常紧凑,高效,占用内存很小,运行效率很好.

关于 Queue:

interface/class	说明
Queue	Queues typically, but do not necessarily,order elements in a FIFO (first-in-first-out) manner

SET-MAP现代诗一首

• 天下人都知道Set,Map不能重复
• 80%人知道hashCode,equals是判断重复的法则
• 40%人知道Set添加重复元素时,旧元素不会被覆盖
• 20%人知道Map添加重复键时,旧键不会被覆盖,而值会覆盖

guava 实用方法:

1. com.google.common.collect.Iterables.concat(Iterable<? extends Iterable<? extends T>>)

Since:

1.0.2, jdk1.5

Author:

feilong

See Also:

Collections, ListUtils, IterableUtils, CollectionUtils, "org.springframework.util.CollectionUtils", "com.google.common.collect.Sets", "com.google.common.collect.Lists", "com.google.common.collect.Queues", "com.google.common.collect.Iterators", "com.google.common.collect.Iterables"

Method Summary

Methods

Modifier and Type	Method and Description
static <O> boolean	addAllIgnoreNull(Collection<O> objectCollection, Iterable<? extends O> iterable) 添加所有的Iterable元素到指定的objectCollection,如果 iterable是null将忽略.
static <T> boolean	addIgnoreNullOrEmpty(Collection<T> objectCollection, T element) 添加 element元素到指定的objectCollection,如果 element 是null或者 empty将忽略.
static <O,I> List<O>	collect(Iterable<I> inputBeanIterable, Class<O> outputListBeanType, String... includePropertyNames) 循环 inputBeanIterable,将每个元素使用转换程成新的 outputListBeanType 类型对象(如有需要只copy传入的includePropertyNames属性) 返回新的list.
static <O,T> List<T>	collect(Iterable<O> inputIterable, Transformer<? super O,? extends T> transformer) 循环 inputIterable,将每个元素使用 transformer 转换成新的对象,返回新的list.
static <O,T> List<T>	collect(Iterator<O> inputIterator, Transformer<? super O,? extends T> transformer) 循环 inputIterator,将每个元素使用 transformer 转换成新的对象 返回新的list.
static <O> O	find(Iterable<O> iterable, Predicate<O> predicate) 迭代查找匹配predicate 的第一个元素并返回.
static <O,V> O	find(Iterable<O> beanIterable, String propertyName, V propertyValue) 找到 iterable中,第一个 propertyName属性名称值是 propertyValue 的对应元素.
static <O> void	forEach(Iterable<O> beanIterable, String propertyName, Object propertyValue) 循环将beanIterable每个元素的每个指定属性 propertyName的值改成 propertyValue.
static <T,O> List<T>	getPropertyValueList(Iterable<O> beanIterable, String propertyName) 循环集合 beanIterable,取到对象指定的属性 propertyName的值,拼成List(ArrayList).
static <K,V,O> Map<K,V>	getPropertyValueMap(Iterable<O> beanIterable, String keyPropertyName, String valuePropertyName) 循环 beanIterable ,以 keyPropertyName属性值为key, valuePropertyName属性值为value,组成map返回.
static <T,O> Set<T>	getPropertyValueSet(Iterable<O> beanIterable, String propertyName) 解析迭代集合 beanIterable ,取到对象指定的属性 propertyName的值,拼成Set(LinkedHashSet).
static <T,O> Map<T,List<O>>	group(Iterable<O> beanIterable, Predicate<O> includePredicate, Transformer<O,T> keyTransformer) 循环 beanIterable,找到符合条件的 includePredicate的元素,将元素使用keyTransformer转成key ,相同值的元素组成list作为value,封装成map返回.
static <T,O> Map<T,List<O>>	group(Iterable<O> beanIterable, String propertyName) 循环 beanIterable,以 元素的 propertyName属性值为key,相同值的元素组成list作为value,封装成map返回.
static <T,O> Map<T,List<O>>	group(Iterable<O> beanIterable, String propertyName, Predicate<O> includePredicate) 循环 beanIterable,找到符合条件的 includePredicate的元素,以元素的 propertyName 属性值为key,相同值的元素组成list作为value,封装成map返回.
static <T,O> Map<T,List<O>>	group(Iterable<O> beanIterable, Transformer<O,T> keyTransformer) 循环 beanIterable,将元素使用keyTransformer转成key,相同值的元素组成list作为value,封装成map返回.
static <T,O> Map<T,O>	groupOne(Iterable<O> beanIterable, String propertyName) 循环 iterable,以元素的 propertyName属性值为key,元素为value,封装成map返回(map只put第一个匹配的元素,后面出现相同的元素将会忽略).
static <O,V> int	indexOf(List<O> list, String propertyName, V propertyValue) 在list中,查找第一个属性 propertyName 值是指定值 propertyValue 对象的索引位置.
static <E> ArrayList<E>	newArrayList() 创建 a mutable, empty ArrayList instance .
static <E> CopyOnWriteArrayList<E>	newCopyOnWriteArrayList() 创建 a mutable, empty CopyOnWriteArrayList instance .
static <E> HashSet<E>	newHashSet() 创建 a mutable, empty newHashSet instance .
static <E> LinkedHashSet<E>	newLinkedHashSet() 创建 a mutable, empty LinkedHashSet instance .
static <E> LinkedList<E>	newLinkedList() 创建 a mutable, empty LinkedList instance .
static <O> List<O>	remove(Collection<O> objectCollection, O... removeElements) 从 objectCollection中 删除removeElements (原集合对象不变).
static <O> List<O>	removeAll(Collection<O> objectCollection, Collection<O> removeCollection) 从 objectCollection中删除所有的 removeCollection (原集合对象不变).
static <O> List<O>	removeAllNull(Collection<O> objectCollection) 从 objectCollection中删除所有的 null元素 (原集合对象不变).
static <O> List<O>	removeDuplicate(Collection<O> objectCollection) 去重,返回没有重复元素的新list (原集合对象不变).
static <O> List<O>	select(Iterable<O> beanIterable, Predicate<O> predicate) 按照指定的 Predicate,返回查询出来的集合.
static <O,V> List<O>	select(Iterable<O> beanIterable, String propertyName, Collection<V> propertyValueList) 循环 beanIterable,获得元素 bean 的propertyName的值,判断是否在propertyValueList 集合中;如果在,将该对象存入list中返回.
static <O,V> List<O>	select(Iterable<O> beanIterable, String propertyName, V... propertyValues) 循环 beanIterable,获得元素 bean的 propertyName的值,判断是否在propertyValues 数组中;如果在,将该对象存入list中返回.
static <O> List<O>	selectRejected(Iterable<O> beanIterable, Predicate<O> predicate) 循环 beanIterable,获得元素 bean,判断是否不匹配predicate,如果不匹配 ,将该对象存入list中返回.
static <O,V> List<O>	selectRejected(Iterable<O> beanIterable, String propertyName, Collection<V> propertyValueList) 循环 beanIterable,获得元素 bean 的 propertyName的值,判断是否不在propertyValueList 集合中;如果不在,将该对象存入list中返回.
static <O,V> List<O>	selectRejected(Iterable<O> beanIterable, String propertyName, V... propertyValues) 循环 beanIterable,获得元素 bean 的 propertyName 属性值都不在 propertyValues 时候的list.

Methods inherited from class java.lang.Object

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

Method Detail

forEach

public static <O> void forEach(Iterable<O> beanIterable,
               String propertyName,
               Object propertyValue)

循环将beanIterable每个元素的每个指定属性 propertyName的值改成 propertyValue.

示例:

对于以下购物车全选的代码:

 
 //找到需要处理的对象list
 List<ShoppingCartLineCommand> toDoNeedChangeCheckedCommandList = select(
                 needChangeCheckedCommandList,
                 toggleCheckStatusShoppingCartLinePredicateBuilder.build(shoppingCartLineCommandList, checkStatus));
 
 // 将状态修改成对应状态
 for (ShoppingCartLineCommand shoppingCartLineCommand : toDoNeedChangeCheckedCommandList){
     shoppingCartLineCommand.setSettlementState(1);
 }
 
 

此时你还可以:

 //找到需要处理的对象list
 List<ShoppingCartLineCommand> toDoNeedChangeCheckedCommandList = select(
                 needChangeCheckedCommandList,
                 toggleCheckStatusShoppingCartLinePredicateBuilder.build(shoppingCartLineCommandList, checkStatus));
 
 // 将状态修改成对应状态
 CollectionsUtil.forEach(toDoNeedChangeCheckedCommandList, "settlementState", 1);
 

说明:

1. 如果 beanIterable 是null或者empty,什么都不做
2. 如果 beanIterable 中有元素是null,将跳过去

Type Parameters:

O - the element type

Parameters:

beanIterable - beanIterable

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

propertyValue - 指定属性的属性值

Throws:

NullPointerException - 如果 propertyName 是null

IllegalArgumentException - 如果 propertyName 是blank

Since:

1.10.2

See Also:

IterableUtils.forEach(Iterable, org.apache.commons.collections4.Closure), BeanPropertyValueChangeClosure

addAllIgnoreNull

public static <O> boolean addAllIgnoreNull(Collection<O> objectCollection,
                           Iterable<? extends O> iterable)

添加所有的Iterable元素到指定的objectCollection,如果 iterable是null将忽略.

示例:

 
 List<String> list = toList("xinge", "feilong1");
 CollectionsUtil.addAllIgnoreNull(list, null); = false
 

重构:

对于以下代码:

 
 private Set<String> getItemComboIds(List<ShoppingCartLineCommand> lines){
     Set<String> set = new HashSet<>();
     if (null != lines && lines.size() > 0){
         for (ShoppingCartLineCommand line : lines){
             if (line.getComboIds() != null){
                 set.addAll(line.getComboIds());
             }
         }
     }
     return set;
 }
 
 

可以重构成:

 
 private Set<String> getItemComboIds(List<ShoppingCartLineCommand> lines){
     if (isNullOrEmpty(lines)){
         return Collections.emptySet();
     }
     Set<String> set = new HashSet<>();
     for (ShoppingCartLineCommand line : lines){
         CollectionsUtil.addAllIgnoreNull(set, line.getComboIds());
     }
     return set;
 }
 

重构之后,方法的复杂度会更小,阅读性更高

Type Parameters:

O - the type of object the Collection contains

Parameters:

objectCollection - the collection to add to, 不能为null

iterable - the iterable of elements to add

Returns:

a boolean 标识 objectCollection 是否改变,如果改变了,返回true.
如果 objectCollection 是null,抛出 NullPointerException
如果 iterable 是null,直接返回false
否则调用CollectionUtils.addAll(Collection, Iterable)

Since:

1.6.3

See Also:

CollectionUtils.addIgnoreNull(Collection, Object), CollectionUtils.addAll(Collection, Iterable), CollectionUtils.addAll(Collection, Iterator)

addIgnoreNullOrEmpty

public static <T> boolean addIgnoreNullOrEmpty(Collection<T> objectCollection,
                               T element)

添加 element元素到指定的objectCollection,如果 element 是null或者 empty将忽略.

重构:

对于以下代码:

 
 List<Object[]> dataList = new ArrayList<>();
 for (T bean : iterable){
     Object[] objectArray = toObjectArray(bean, propertyNameList);
     if (isNotNullOrEmpty(objectArray)){
         dataList.add(objectArray);
     }
 }
 return dataList;
 
 

可以重构成:

 
 List<Object[]> dataList = new ArrayList<>();
 for (T bean : iterable){
     addIgnoreNullOrEmpty(dataList, toObjectArray(bean, propertyNameList));
 }
 return dataList;
 

重构之后,方法的复杂度会更小,阅读性更高

Type Parameters:

T - the generic type

Parameters:

objectCollection - the collection to add to, 不能为null

element - element to add

Returns:

a boolean 标识 objectCollection 是否改变,如果改变了,返回true.
如果 objectCollection 是null,抛出 NullPointerException
如果 element 是null 或者 empty,直接返回false
否则调用objectCollection.add(object)

Since:

1.8.2

See Also:

CollectionUtils.addIgnoreNull(Collection, Object)

indexOf

public static <O,V> int indexOf(List<O> list,
                String propertyName,
                V propertyValue)

在list中,查找第一个属性 propertyName 值是指定值 propertyValue 对象的索引位置.

示例:

 List<User> list = new ArrayList<>();
 list.add(new User("张飞", 23));
 list.add(new User("关羽", 24));
 list.add(new User("刘备", 25));
 
 CollectionsUtil.indexOf(list, "name", "张飞")                          =   0
 
 CollectionsUtil.indexOf(null, "age", 24)                             =   -1
 CollectionsUtil.indexOf(new ArrayList<User>(), "age", 24)    =   -1
 

说明:

1. 常用于 浏览历史记录,当前的商品id是否在历史记录中第一条位置,如果是,可能就不会操作Cookie,诸如此类的操作

Type Parameters:

O - the generic type

V - the generic type

Parameters:

list - the list

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

propertyValue - 指定属性的属性值

Returns:

如果 list是null 或者 empty,返回 -1
如果指定属性propertyName的值 propertyValue在 list 查找不到,返回 -1

Throws:

NullPointerException - 如果 propertyName 是null

IllegalArgumentException - 如果 propertyName 是blank

Since:

1.5.5

See Also:

ListUtils.indexOf(List, Predicate), BeanPredicateUtil.equalPredicate(String, Object)

removeAll

public static <O> List<O> removeAll(Collection<O> objectCollection,
                    Collection<O> removeCollection)

从 objectCollection中删除所有的 removeCollection (原集合对象不变).

说明:

1. 返回剩余的集合 (原集合对象objectCollection不变),如果你不想修改 objectCollection的话,不能直接调用 collection.removeAll(remove);,这个方法非常有用.
2. 底层实现是调用的 ListUtils.removeAll(Collection, Collection),将不是removeElement的元素加入到新的list返回.

示例:

场景: 从list中删除 "feilong2","feilong1"元素

 List<String> list = toList("xinge", "feilong1", "feilong2", "feilong2");
 List<String> removeList = CollectionsUtil.removeAll(list, toList("feilong2", "feilong1"));
 

返回:

 ["xinge"]
 

Type Parameters:

O - the generic type

Parameters:

objectCollection - the collection from which items are removed (in the returned collection)

removeCollection - the items to be removed from the returned collection

Returns:

从 objectCollection中排除掉 removeCollection 元素的新的 list

Throws:

NullPointerException - 如果 objectCollection 是null,或者 removeCollection 是null

Since:

Commons Collections 4, 1.0.8

See Also:

ListUtils.removeAll(Collection, Collection)

removeAllNull

public static <O> List<O> removeAllNull(Collection<O> objectCollection)

从 objectCollection中删除所有的 null元素 (原集合对象不变).

说明:

1. 返回剩余的集合 (原集合对象objectCollection不变),如果你不想修改 objectCollection的话,不能直接调用 collection.removeAll(remove);,这个方法非常有用.
2. 底层实现是调用的 ListUtils.removeAll(Collection, Collection),将不是removeElement的元素加入到新的list返回.

示例:

场景: 从list中删除 null 元素

 List<String> list = toList("xinge", null, "feilong2", null, "feilong2");
 List<String> removeList = CollectionsUtil.removeAllNull(list);
 

返回:

 "xinge", "feilong2", "feilong2"
 

Type Parameters:

O - the generic type

Parameters:

objectCollection - the collection from which items are removed (in the returned collection)

Returns:

从 objectCollection中排除掉 null 元素的新的 list

Throws:

NullPointerException - 如果 objectCollection 是null

Since:

Commons Collections 4, 1.11.0

See Also:

ListUtils.removeAll(Collection, Collection)

remove

@SafeVarargs
public static <O> List<O> remove(Collection<O> objectCollection,
                             O... removeElements)

从 objectCollection中 删除removeElements (原集合对象不变).

说明:

1. 返回剩余的集合 (原集合对象不变),这个方法非常有用,如果你不想修改 collection的话,不能调用 collection.remove(removeElements);.
2. 底层实现是调用的 ListUtils.removeAll(Collection, Collection),将不是removeElements 的元素加入到新的list返回.

示例:

 List<String> list = new ArrayList<>();
 list.add("xinge");
 list.add("feilong1");
 list.add("feilong2");
 list.add("feilong2");
 
 LOGGER.info(JsonUtil.format(CollectionsUtil.remove(list, "feilong2")));
 

返回:

 ["xinge","feilong1"]
 

此时,原来的list不变:

 LOGGER.info(JsonUtil.format(list));
 

输出 :

 ["xinge","feilong1","feilong2","feilong2"]
 

Type Parameters:

O - the generic type

Parameters:

objectCollection - the object collection

removeElements - 需要被删除的元素

Returns:

a List containing all the elements of c except any elements that also occur in remove.

Throws:

NullPointerException - 如果 objectCollection 是null

Since:

Commons Collections 4, 1.0.8, 1.10.7 change param to Varargs

See Also:

removeAll(Collection, Collection), ListUtils.removeAll(Collection, Collection)

removeDuplicate

public static <O> List<O> removeDuplicate(Collection<O> objectCollection)

去重,返回没有重复元素的新list (原集合对象不变).

示例:

 List<String> list = new ArrayList<>();
 list.add("feilong1");
 list.add("feilong2");
 list.add("feilong2");
 list.add("feilong3");
 
 LOGGER.info(JsonUtil.format(CollectionsUtil.removeDuplicate(list)));
 

返回:

 ["feilong1","feilong2","feilong3"]
 

注意:

1. 如果原 objectCollection 是有序的,那么返回的结果参照原 objectCollection元素顺序
2. 原 objectCollection不变

Type Parameters:

O - the generic type

Parameters:

objectCollection - the object collection

Returns:

如果 objectCollection 是null或者empty,返回 Collections.emptyList()
否则先转换成 LinkedHashSet,再转换成ArrayList返回

See Also:

LinkedHashSet.LinkedHashSet(Collection), ConvertUtil.toList(Collection), IterableUtils.uniqueIterable(Iterable), http://www.oschina.net/code/snippet_117714_2991?p=2#comments

getPropertyValueList

public static <T,O> List<T> getPropertyValueList(Iterable<O> beanIterable,
                                 String propertyName)

循环集合 beanIterable,取到对象指定的属性 propertyName的值,拼成List(ArrayList).

示例:

场景: 获取user list每个元素的id属性值,组成新的list返回

 
 List<User> list = toList(//
                 new User(2L),
                 new User(5L),
                 new User(5L));
 
 List<Long> resultList = CollectionsUtil.getPropertyValueList(list, "id");
 LOGGER.debug(JsonUtil.format(resultList));
 
 

返回:

 [2,5,5]
 

对于参数 propertyName:

对于以下的数据结构:

 
 //***************list****************************************
 List<UserAddress> userAddresseList = new ArrayList<>();
 
 UserAddress userAddress = new UserAddress();
 userAddress.setAddress("中南海");
 userAddresseList.add(userAddress);
 
 //***************map****************************************
 Map<String, String> attrMap = new HashMap<>();
 attrMap.put("蜀国", "赵子龙");
 attrMap.put("魏国", "张文远");
 attrMap.put("吴国", "甘兴霸");
 
 //---------------------------------------------------------------
 UserInfo userInfo1 = new UserInfo();
 userInfo1.setAge(28);
 
 User user1 = new User(2L);
 user1.setLoves(new String[] { "sanguo1", "xiaoshuo1" });
 user1.setUserInfo(userInfo1);
 user1.setAttrMap(attrMap);
 user1.setUserAddresseList(userAddresseList);
 
 //---------------------------------------------------------------
 UserInfo userInfo2 = new UserInfo();
 userInfo2.setAge(null);
 
 User user2 = new User(3L);
 user2.setLoves(new String[] { "sanguo2", "xiaoshuo2" });
 user2.setUserInfo(userInfo2);
 user2.setAttrMap(attrMap);
 user2.setUserAddresseList(userAddresseList);
 
 List<User> userList = toList(user1,user2);
 

以下情况:

 //数组,取userList 每个元素的 loves属性第2个元素的值
 CollectionsUtil.getPropertyValueList(userList, "loves[1]")                   =   ["xiaoshuo1","xiaoshuo2"]

 //级联对象,取userList 每个元素的 userInfo属性的 age 属性的值
 CollectionsUtil.getPropertyValueList(userList, "userInfo.age")               =   [28,null]
 
 //Map,取userList 每个元素的 attrMap属性中的key是 "蜀国" 的值
 CollectionsUtil.getPropertyValueList(userList, "attrMap(蜀国)")                =   ["赵子龙","赵子龙"]
 
 //集合,取userList 每个元素的 userAddresseList属性中的第一个元素
 CollectionsUtil.getPropertyValueList(userList, "userAddresseList[0]")        = [{"address": "中南海"},{"address": "中南海"}]
 

关于参数 beanIterable

支持以下类型:

bean Iterable

诸如List<User>,Set<User>等

map Iterable

比如 List<Map<String, String>> 示例:

 List<Map<String, String>> list = newArrayList();
 list.add(toMap("key", "value1"));
 list.add(toMap("key", "value2"));
 list.add(toMap("key", "value3"));
 
 List<String> resultList = CollectionsUtil.getPropertyValueList(list, "(key)");
 assertThat(resultList, contains("value1", "value2", "value3"));
 

list Iterable

比如 List<List<String>> 示例:

 List<List<String>> list = newArrayList();
 list.add(toList("小明", "18"));
 list.add(toList("小宏", "18"));
 list.add(toList("小振", "18"));
 
 List<String> resultList = CollectionsUtil.getPropertyValueList(list, "[0]");
 assertThat(resultList, contains("小明", "小宏", "小振"));
 

数组 Iterable

比如 List<String[]> 示例:

 List<String[]> list = newArrayList();
 list.add(toArray("三国", "水浒"));
 list.add(toArray("西游", "金瓶梅"));
 
 List<String> resultList = CollectionsUtil.getPropertyValueList(list, "[0]");
 assertThat(resultList, contains("三国", "西游"));
 

Type Parameters:

T - 返回集合类型 generic type

O - 可迭代对象类型 generic type

Parameters:

beanIterable - 支持

• bean Iterable,比如List<User>,Set<User>等
• map Iterable,比如List<Map<String, String>>
• list Iterable , 比如 List<List<String>>
• 数组 Iterable ,比如 List<String[]>

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:

如果参数 beanIterable是null或者empty,会返回empty ArrayList
如果 propertyName 是null,抛出 NullPointerException
如果 propertyName 是blank,抛出 IllegalArgumentException

Since:

jdk1.5

See Also:

PropertyValueObtainer.getPropertyValueCollection(Iterable, String, Collection)

getPropertyValueSet

public static <T,O> Set<T> getPropertyValueSet(Iterable<O> beanIterable,
                               String propertyName)

解析迭代集合 beanIterable ,取到对象指定的属性 propertyName的值,拼成Set(LinkedHashSet).

说明:

1. 返回的是 LinkedHashSet,顺序是参数 beanIterable 元素的顺序

示例:

 List<User> list = new ArrayList<>();
 list.add(new User(2L));
 list.add(new User(5L));
 list.add(new User(5L));
 
 LOGGER.info(JsonUtil.format(CollectionsUtil.getPropertyValueSet(list, "id")));
 

返回:

 [2,5]
 

Type Parameters:

T - the generic type

O - the generic type

Parameters:

beanIterable - 支持

• bean Iterable,比如List<User>,Set<User>等
• map Iterable,比如List<Map<String, String>>
• list Iterable , 比如 List<List<String>>
• 数组 Iterable ,比如 List<String[]>

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:

如果参数 beanIterable是null或者empty,会返回empty LinkedHashSet
如果 propertyName 是null,抛出 NullPointerException
如果 propertyName 是blank,抛出 IllegalArgumentException

Since:

1.0.8

See Also:

PropertyValueObtainer.getPropertyValueCollection(Iterable, String, Collection)

getPropertyValueMap

public static <K,V,O> Map<K,V> getPropertyValueMap(Iterable<O> beanIterable,
                                   String keyPropertyName,
                                   String valuePropertyName)

循环 beanIterable ,以 keyPropertyName属性值为key, valuePropertyName属性值为value,组成map返回.

说明:

1. 返回的是 LinkedHashMap,顺序是参数 beanIterable 元素的顺序
2. 如果有元素 keyPropertyName属性值相同,那么后面的值会覆盖前面的值

示例:

 List<User> list = new ArrayList<>();
 list.add(new User("张飞", 23));
 list.add(new User("关羽", 24));
 list.add(new User("刘备", 25));
 
 LOGGER.info(JsonUtil.format(CollectionsUtil.getPropertyValueMap(list, "name", "age")));
 

返回:

 {
 "张飞": 23,
 "关羽": 24,
 "刘备": 25
 }
 

如果有元素 keyPropertyName属性值相同,那么后面的值会覆盖前面的值

 List<User> list = new ArrayList<>();
 list.add(new User("张飞", 23));
 list.add(new User("关羽", 24));
 list.add(new User("张飞", 25));
 
 LOGGER.info(JsonUtil.format(CollectionsUtil.getPropertyValueMap(list, "name", "age")));
 

返回:

 {
 "张飞": 25,
 "关羽": 24,
 }
 

Type Parameters:

K - the key type

V - the value type

O - 可迭代对象类型 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,取到的值将作为返回的map的key,Possibly indexed and/or nested name of the property to be modified,参见 propertyName

valuePropertyName - 泛型O对象指定的属性名称,取到的值将作为返回的map的value,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 keyPropertyName 是null,抛出 NullPointerException
如果 keyPropertyName 是blank,抛出 IllegalArgumentException
如果 valuePropertyName 是null,抛出 NullPointerException
如果 valuePropertyName 是blank,抛出 IllegalArgumentException

See Also:

PropertyUtil.getProperty(Object, String)

find

public static <O,V> O find(Iterable<O> beanIterable,
           String propertyName,
           V propertyValue)

找到 iterable中,第一个 propertyName属性名称值是 propertyValue 的对应元素.

示例:

场景: 从list中查找name是 关羽 的User对象

 List<User> list = new ArrayList<>();
 list.add(new User("张飞", 23));
 list.add(new User("关羽", 24));
 list.add(new User("刘备", 25));
 list.add(new User("关羽", 50));
 
 LOGGER.info(JsonUtil.format(CollectionsUtil.find(list, "name", "关羽")));
 

返回:

 {
 "age": 24,
 "name": "关羽"
 }
 

说明:

1. 返回第一个匹配对象

Type Parameters:

O - the generic type

V - the value 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

propertyValue - 指定的值

Returns:

如果 iterable是null, 返回null
如果 propertyName 是null,抛出 NullPointerException
如果 propertyName 是blank,抛出 IllegalArgumentException
如果 iterable中没有相关元素的属性propertyName 值是propertyValue,返回null

See Also:

find(Iterable, Predicate), BeanPredicateUtil.equalPredicate(String, Object)

find

public static <O> O find(Iterable<O> iterable,
         Predicate<O> predicate)

迭代查找匹配predicate 的第一个元素并返回.

示例:

场景: 从list中查找name是 关羽,并且 age等于30的User对象

 List<User> list = toList(//
                 new User("张飞", 23),
                 new User("关羽", 24),
                 new User("刘备", 25),
                 new User("关羽", 30));
 
 Map<String, Object> map = new HashMap<>();
 map.put("name", "关羽");
 map.put("age", 30);
 
 Predicate<User> predicate = BeanPredicateUtil.equalPredicate(map);
 
 User user = CollectionsUtil.find(list, predicate);
 LOGGER.debug(JsonUtil.format(user));
 

返回:

 {
 "age": 30,
 "name": "关羽"
 }
 

说明:

1. 返回第一个匹配对象

Type Parameters:

O - the generic type

Parameters:

iterable - the iterable to search, may be null

predicate - the predicate to use, may not be null

Returns:

如果 predicate 是 null,将抛出NullPointerException
如果 iterable是null, 返回null
如果 iterable中没有相关元素匹配 predicate,返回null

Since:

1.5.5

See Also:

IterableUtils.find(Iterable, Predicate)

select

@SafeVarargs
public static <O,V> List<O> select(Iterable<O> beanIterable,
                               String propertyName,
                               V... propertyValues)

循环 beanIterable,获得元素 bean的 propertyName的值,判断是否在propertyValues 数组中;如果在,将该对象存入list中返回.

注意:

查询的结果的顺序按照原来 beanIterable里面的顺序,和参数 propertyValues 无关,如果你需要结果里面的元素按照指定的propertyValues 顺序排序的话,可以将结果再调用SortUtil.sortListByFixedOrderPropertyValueArray(List, String, Object...)

示例:

 List<User> list = new ArrayList<>();
 list.add(new User("张飞", 23));
 list.add(new User("关羽", 24));
 list.add(new User("刘备", 25));
 
 String[] array = { "刘备", "关羽" };
 LOGGER.info(JsonUtil.format(CollectionsUtil.select(list, "name", array)));
 
 

返回:

       [{
               "age": 24,
               "name": "关羽"
           },{
               "age": 25,
               "name": "刘备"
       }]
 

Type Parameters:

O - the generic type

V - the value 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

propertyValues - the values

Returns:

如果 beanIterable 是null或者empty,返回 Collections.emptyList()
如果 propertyName 是null,抛出 NullPointerException
如果 propertyName 是blank,抛出 IllegalArgumentException
如果 propertyValues 是null,返回 new ArrayList<O>

See Also:

BeanPredicateUtil.containsPredicate(String, Object...)

select

public static <O,V> List<O> select(Iterable<O> beanIterable,
                   String propertyName,
                   Collection<V> propertyValueList)

循环 beanIterable,获得元素 bean 的propertyName的值,判断是否在propertyValueList 集合中;如果在,将该对象存入list中返回.

说明:

1. 查询的结果的顺序按照原来 beanIterable里面的顺序,和参数 propertyValueList 无关,如果你需要结果里面的元素按照指定的 propertyValueList顺序排序的话,可以将结果再调用SortUtil.sortListByFixedOrderPropertyValueList(List, String, List)
2. 和该方法正好相反的是 selectRejected(Iterable, String, Collection)

示例:

场景: 查询 name属性是"张飞"或者是"刘备"的 User list

 List<User> list = new ArrayList<>();
 list.add(new User("张飞", 23));
 list.add(new User("关羽", 24));
 list.add(new User("刘备", 25));
 
 List<String> propertyValueList = new ArrayList<>();
 propertyValueList.add("张飞");
 propertyValueList.add("刘备");
 LOGGER.info(JsonUtil.format(CollectionsUtil.select(list, "name", propertyValueList)));
 

返回:

    [{
                "age": 23,
                "name": "张飞"
            },{
                "age": 25,
                "name": "刘备"
     }]
 
 

重构:

对于以下代码:

 
 // 当前店铺 的物流方式Id set
 Set<Long> distributionModeIdSet = new HashSet<>();
 for (TemeplateDistributionMode tdCmd : temeplateDistributionModeList){
     distributionModeIdSet.add(tdCmd.getDistributionModeId());
 }
 
 // 拿到所有的物流方式 列表
 List<DistributionCommand> distributionCommandList = freigthMemoryManager.getDistributionList();
 
 // 根据 物流方式ID 找出 支持本商铺的 DistributionCommand
 List<DistributionCommand> curShopDistributionCommandList = new ArrayList<>();
 
 for (Long modeId : distributionModeIdSet){
     for (DistributionCommand distributionCmd : distributionCommandList){
         if (modeId.equals(distributionCmd.getDistributionModeId())){
             curShopDistributionCommandList.add(distributionCmd);
         }
     }
 }
 

可以重构成:

 // 当前店铺 的物流方式Id set
 Set<Long> distributionModeIdSet = CollectionsUtil.getPropertyValueSet(temeplateDistributionModeList, "distributionModeId");
 // 拿到所有的物流方式 列表
 List<DistributionCommand> distributionCommandList = freigthMemoryManager.getDistributionList();
 
 // 根据 物流方式ID 找出 支持本商铺的 DistributionCommand
 List<DistributionCommand> curShopDistributionCommandList = CollectionsUtil.select(distributionCommandList, "distributionModeId", distributionModeIdSet);
 

Type Parameters:

O - the generic type

V - the value 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

propertyValueList - the values

Returns:

如果 beanIterable 是null或者empty,返回 Collections.emptyList()
如果 propertyName 是null,抛出 NullPointerException
如果 propertyName 是blank,抛出 IllegalArgumentException
否则调用 select(Iterable, Predicate)

Since:

1.5.0

See Also:

select(Iterable, Predicate), BeanPredicateUtil.containsPredicate(String, Collection)

select

public static <O> List<O> select(Iterable<O> beanIterable,
                 Predicate<O> predicate)

按照指定的 Predicate,返回查询出来的集合.

说明:

1. 和该方法正好相反的是 selectRejected(Iterable, Predicate)

示例1:

场景: 查找等于 1的元素

 List<Long> list = new ArrayList<>();
 list.add(1L);
 list.add(1L);
 list.add(2L);
 list.add(3L);
 LOGGER.info(JsonUtil.format(CollectionsUtil.select(list, new EqualPredicate<Long>(1L))));
 

返回:

 [1,1]
 

示例2:

场景: 查找大于 10的元素

 Comparator<Integer> comparator = ComparatorUtils.naturalComparator();
 Predicate<Integer> predicate = new ComparatorPredicate<Integer>(10, comparator, Criterion.LESS);
 
 List<Integer> select = CollectionsUtil.select(toList(1, 5, 10, 30, 55, 88, 1, 12, 3), predicate);
 LOGGER.debug(JsonUtil.format(select, 0, 0));
 

返回:

 [30,55,88,12]
 

Type Parameters:

O - the generic type

Parameters:

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

predicate - 接口封装了对输入对象的判断,返回true或者false,可用的实现类有

• EqualPredicate
• IdentityPredicate
• FalsePredicate
• TruePredicate
• ....

Returns:

如果 beanIterable 是null或者empty,返回 Collections.emptyList()
否则返回 CollectionUtils.select(Iterable, Predicate)

See Also:

CollectionUtils.select(Iterable, Predicate)

selectRejected

@SafeVarargs
public static <O,V> List<O> selectRejected(Iterable<O> beanIterable,
                                       String propertyName,
                                       V... propertyValues)

循环 beanIterable,获得元素 bean 的 propertyName 属性值都不在 propertyValues 时候的list.

示例:

场景: 查询name 不是刘备 也不是张飞的 User list元素

 
 List<User> list = new ArrayList<>();
 list.add(new User("张飞", 23));
 list.add(new User("关羽", 24));
 list.add(new User("刘备", 25));
 
 List<User> selectRejected = CollectionsUtil.selectRejected(list, "name", "刘备", "张飞");
 LOGGER.info(JsonUtil.format(selectRejected));
 
 

返回:

 [{
 "age": 24,
 "name": "关羽"
 }]
 

Type Parameters:

O - the generic type

V - the value 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

propertyValues - the values

Returns:

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

See Also:

BeanPredicateUtil.containsPredicate(String, Object...), selectRejected(Iterable, Predicate)

selectRejected

public static <O,V> List<O> selectRejected(Iterable<O> beanIterable,
                           String propertyName,
                           Collection<V> propertyValueList)

循环 beanIterable,获得元素 bean 的 propertyName的值,判断是否不在propertyValueList 集合中;如果不在,将该对象存入list中返回.

示例:

场景: 查询 name属性是不是"张飞",也不是"刘备"的 User list

 
 List<User> list = new ArrayList<>();
 list.add(new User("张飞", 23));
 list.add(new User("关羽", 24));
 list.add(new User("刘备", 25));
 
 List<String> propertyValueList = new ArrayList<>();
 propertyValueList.add("张飞");
 propertyValueList.add("刘备");
 LOGGER.info(JsonUtil.format(CollectionsUtil.selectRejected(list, "name", propertyValueList)));
 
 

返回:

 [{
 "age": 24,
 "name": "关羽"
 }]
 

说明:

1. 和该方法正好相反的是 select(Iterable, String, Collection)

Type Parameters:

O - the generic type

V - the value 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

propertyValueList - the values

Returns:

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

Since:

1.5.0

See Also:

BeanPredicateUtil.containsPredicate(String, Collection), selectRejected(Iterable, Predicate)

selectRejected

public static <O> List<O> selectRejected(Iterable<O> beanIterable,
                         Predicate<O> predicate)

循环 beanIterable,获得元素 bean,判断是否不匹配predicate,如果不匹配 ,将该对象存入list中返回.

说明:

1. 和该方法正好相反的是 select(Iterable, Predicate)

示例:

场景: 从list中查找不等于1的元素

 List<Long> list = toList(1L, 1L, 2L, 3L);
 CollectionsUtil.selectRejected(list, new EqualPredicate<Long>(1L))
 

返回:

 2L, 3L
 

Type Parameters:

O - the generic type

Parameters:

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

predicate - the predicate

Returns:

如果 beanIterable 是null或者empty,返回 Collections.emptyMap()

Since:

1.4.0

See Also:

CollectionUtils.selectRejected(Iterable, Predicate)

collect

public static <O,T> List<T> collect(Iterable<O> inputIterable,
                    Transformer<? super O,? extends T> transformer)

循环 inputIterable,将每个元素使用 transformer 转换成新的对象,返回新的list.

示例:

 
 List<String> list = new ArrayList<>();
 list.add("xinge");
 list.add("feilong1");
 list.add("feilong2");
 list.add("feilong2");
 
 Transformer<String, Object> nullTransformer = TransformerUtils.nullTransformer();
 List<Object> collect = CollectionsUtil.collect(list, nullTransformer);
 LOGGER.info(JsonUtil.format(collect, 0, 0));
 
 

返回:

 [null,null,null,null]
 

更多的,使用这个方法来处理两个不同类型的转换:

比如购物车功能,有游客购物车CookieShoppingCartLine以及内存购物车对象 ShoppingCartLineCommand,两个数据结构部分元素相同,
用户登陆需要把cookie中的购物车转成内存购物车ShoppingCartLineCommand list,这时我们可以先创建ToShoppingCartLineCommandTransformer

代码示例:

 
 class ToShoppingCartLineCommandTransformer implements Transformer<CookieShoppingCartLine, ShoppingCartLineCommand>{
 
     private static final String[] COPY_PROPERTY_NAMES = {"skuId","extentionCode","quantity","createTime","settlementState","lineGroup" };
 
     public ShoppingCartLineCommand transform(CookieShoppingCartLine cookieShoppingCartLine){
         // 将cookie中的购物车 转换为 shoppingCartLineCommand
         ShoppingCartLineCommand shoppingLineCommand = new ShoppingCartLineCommand();
         PropertyUtil.copyProperties(shoppingLineCommand, cookieShoppingCartLine, COPY_PROPERTY_NAMES);
 
         shoppingLineCommand.setId(cookieShoppingCartLine.getId());
         shoppingLineCommand.setGift(null == cookieShoppingCartLine.getIsGift() ? false : cookieShoppingCartLine.getIsGift());
 
         return shoppingLineCommand;
     }
 }
 
 

然后调用:

 
 public List<ShoppingCartLineCommand> load(HttpServletRequest request){
     // 获取cookie中的购物车行集合
     List<CookieShoppingCartLine> cookieShoppingCartLineList = getCookieShoppingCartLines(request);
     if (isNullOrEmpty(cookieShoppingCartLineList)){
         return null;
     }
 
     return CollectionsUtil.collect(cookieShoppingCartLineList, new ToShoppingCartLineCommandTransformer());
 }
 

Type Parameters:

O - the type of object in the input collection

T - the type of object in the output collection

Parameters:

inputIterable - the inputIterable to get the input from

transformer - the transformer to use, may be null

Returns:

如果 inputIterable 是null,返回 null
如果 transformer 是null,返回 empty list

Since:

1.5.5

See Also:

CollectionUtils.collect(Iterable, Transformer), CollectionUtils.transform(Collection, Transformer)

collect

public static <O,I> List<O> collect(Iterable<I> inputBeanIterable,
                    Class<O> outputListBeanType,
                    String... includePropertyNames)

循环 inputBeanIterable,将每个元素使用转换程成新的 outputListBeanType 类型对象(如有需要只copy传入的includePropertyNames属性) 返回新的list.

示例:

已知有以下两个类 User 和 Customer

 
 public class User{
 
     // The id. 
     private Long id = 0L;
 
     //** The name. 
     private String name = "feilong";
 
     //** 年龄. 
     private Integer age;
 
     //setter /getter
 
     public User(Long id, String name){
         this.id = id;
         this.name = name;
     }
 
 }
 
 

 
 public class Customer{
 
     //** The id. 
     private long id;
 
     //* The name. 
     private String name;
 
     //setter /getter
 
 }
 
 

此时有以下的 List<User> 需要转换成List<Customer>

 
 List<User> list = toList(//
                 new User(23L, "张飞"),
                 new User(24L, "关羽"),
                 new User(25L, "刘备"));
 

以前你需要如此这般写:

 List<Customer> customerList = new ArrayList<>();
 for (User user : list){
     Customer customer = new Customer();
     customer.setId(user.getId());
     customer.setName(user.getName());
     customerList.add(customer);
 }
 

如果属性很多,书写代码很繁琐

此时你可以这么写:

  List<Customer> customerList = CollectionsUtil.collect(list, Customer.class);
 

一行代码搞定集合转换问题

如果你只想转换id属性,你可以:

  List<Customer> customerList = CollectionsUtil.collect(list, Customer.class,"id");
 

说明:

1. outputListBeanType 需要有默认的构造函数

Type Parameters:

O - the generic type

I - the generic type

Parameters:

inputBeanIterable - 输入的input bean Iterable

outputListBeanType - 要转成Bean list的类型.

includePropertyNames - 包含的属性数组名字数组,(can be nested/indexed/mapped/combo),
如果是null或者empty,那么复制所有的属性

1. 如果传入的includePropertyNames,含有 inputBeanIterable bean 没有的属性名字,将会抛出异常
2. 如果传入的includePropertyNames,含有 inputBeanIterable bean有,但是outputListBeanType没有的属性名字,会抛出异常,seecopyProperties Line2078

Returns:

如果 inputBeanIterable 是null,返回 null
如果 inputBeanIterable 中有元素是null,那么返回的list对应位置的元素也是null
如果 outputListBeanType 是null,抛出 NullPointerException

Since:

1.10.1

collect

public static <O,T> List<T> collect(Iterator<O> inputIterator,
                    Transformer<? super O,? extends T> transformer)

循环 inputIterator,将每个元素使用 transformer 转换成新的对象 返回新的list.

示例:

场景: 一个简单的将list中的所有元素转成null

 List<String> list = toList("xinge", "feilong1", "feilong2", "feilong2");
 
 Transformer<String, Object> nullTransformer = TransformerUtils.nullTransformer();
 List<Object> collect = CollectionsUtil.collect(list.iterator(), nullTransformer);
 LOGGER.info(JsonUtil.format(collect, 0, 0));
 

返回:

 [null,null,null,null]
 

Type Parameters:

O - the type of object in the output collection

T - the type of object in the input collection

Parameters:

inputIterator - the iterator to get the input from

transformer - the transformer to use, may be null

Returns:

如果 inputIterator 是null,返回 null
如果 transformer 是null,返回 new ArrayList<>

Since:

1.5.5

See Also:

CollectionUtils.collect(java.util.Iterator, Transformer)

group

public static <T,O> Map<T,List<O>> group(Iterable<O> beanIterable,
                         String propertyName)

循环 beanIterable,以 元素的 propertyName属性值为key,相同值的元素组成list作为value,封装成map返回.

说明:

1. 返回的LinkedHashMap,key是 beanIterable中的元素对象中 propertyName的值,value是beanIterable 中的元素对象;
2. 顺序是 beanIterable propertyName的值顺序,如果需要排序,可自行调用 SortUtil.sortMapByKeyAsc(Map), SortUtil.sortMapByKeyDesc(Map), SortUtil.sortMapByValueAsc(Map), SortUtil.sortMapByValueDesc(Map)或者, SortUtil.sortMap(Map, java.util.Comparator)
3. 属性propertyName值相同的元素,组成集合 list
4. 如果value只需要单值的话,可以调用 groupOne(Iterable, String)方法

示例:

 List<User> list = toList(
                 new User("张飞", 23),
                 new User("刘备", 25),
                 new User("刘备", 30));
 
 Map<String, List<User>> map = CollectionsUtil.group(list, "name");
 LOGGER.debug(JsonUtil.format(map));
 

返回:

    {
        "张飞": [ {
            "age": 23,
            "name": "张飞",
        }],
        "刘备": [
            {
                "age": 25,
                "name": "刘备",
            },
            {
                "age": 30,
                "name": "刘备",
            }
        ]
    }
 

Type Parameters:

T - 注意,此处的T是属性值,Object类型,如果从excel中读取的类型是String,那么不能简简单单的使用Integer来接收,不能强制转换

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 Collections.emptyMap()
如果 propertyName 是null,抛出 NullPointerException
如果 propertyName 是blank,抛出 IllegalArgumentException

Since:

1.0.8

See Also:

group(Iterable, String, Predicate)

group

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

循环 beanIterable,找到符合条件的 includePredicate的元素,以元素的 propertyName 属性值为key,相同值的元素组成list作为value,封装成map返回.

说明:

1. 返回的LinkedHashMap,key是 beanIterable中的元素对象中 propertyName的值,value是beanIterable 中的元素对象;
2. 顺序是 beanIterable propertyName的值顺序,如果需要排序,可自行调用 SortUtil.sortMapByKeyAsc(Map), SortUtil.sortMapByKeyDesc(Map), SortUtil.sortMapByValueAsc(Map), SortUtil.sortMapByValueDesc(Map)或者, SortUtil.sortMap(Map, java.util.Comparator)

示例:

场景: 将age > 20的User,按照name 进行 group

        List<User> list = new ArrayList<>();
        list.add(new User("张飞", 10));
        list.add(new User("张飞", 28));
        list.add(new User("刘备", 32));
        list.add(new User("刘备", 30));
        list.add(new User("刘备", 10));

        Map<String, List<User>> map = CollectionsUtil.group(list, "name", new Predicate<User>(){

            @Override
            public boolean evaluate(User user){
                return user.getAge() > 20;
            }
        });
        LOGGER.info(JsonUtil.format(map));
 

返回:

    {
        "张飞": [{
            "age": 28,
            "name": "张飞"
        }],
        "刘备": [{
                "age": 32,
                "name": "刘备"
            },{
                "age": 30,
                "name": "刘备"
            }
        ]
    }
 

当然,对于上述代码,你还可以优化成:

 Predicate<User> comparatorPredicate = BeanPredicateUtil.comparatorPredicate("age", 20, Criterion.LESS);
 Map<String, List<User>> map = CollectionsUtil.group(list, "name", comparatorPredicate);
 

参见 BeanPredicateUtil.comparatorPredicate(String, Comparable, org.apache.commons.collections4.functors.ComparatorPredicate.Criterion)

Type Parameters:

T - 注意,此处的T是属性值,Object类型,如果从excel中读取的类型是String,那么不能简简单单的使用Integer来接收,不能强制转换

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 Collections.emptyMap()
如果 propertyName 是null,抛出 NullPointerException
如果 propertyName 是blank,抛出 IllegalArgumentException
如果没有任何element match includePredicate,返回 empty LinkedHashMap
如果 includePredicate 是null,那么以所有的元素进行分组

Since:

1.5.5

See Also:

PropertyUtil.getProperty(Object, String), groupOne(Iterable, String)

group

public static <T,O> Map<T,List<O>> group(Iterable<O> beanIterable,
                         Transformer<O,T> keyTransformer)

循环 beanIterable,将元素使用keyTransformer转成key,相同值的元素组成list作为value,封装成map返回.

说明:

1. 返回的LinkedHashMap,key是 beanIterable中的元素 使用keyTransformer转换的值,value是 beanIterable中的元素对象(相同key值,组成list);
2. 返回的LinkedHashMap顺序,是 beanIterable 元素顺序,如果需要排序,可自行调用 SortUtil.sortMapByKeyAsc(Map), SortUtil.sortMapByKeyDesc(Map), SortUtil.sortMapByValueAsc(Map), SortUtil.sortMapByValueDesc(Map)或者, SortUtil.sortMap(Map, java.util.Comparator)

示例:

场景: 从user list中,提取user的姓名的姓为key,user组成list,返回map

 
 User mateng55 = new User("马腾", 55);
 User machao28 = new User("马超", 28);
 User madai27 = new User("马岱", 27);
 User maxiu25 = new User("马休", 25);
 User zhangfei28 = new User("张飞", 28);
 User liubei32 = new User("刘备", 32);
 User guanyu50 = new User("关羽", 50);
 User guanping32 = new User("关平", 32);
 User guansuo31 = new User("关索", 31);
 User guanxing20 = new User("关兴", 18);
 
 //---------------------------------------------------------------
 List<User> list = toList(mateng55, machao28, madai27, maxiu25, zhangfei28, liubei32, guanyu50, guanping32, guansuo31, guanxing20);
 
 //---------------------------------------------------------------
 
 Map<String, List<User>> map = CollectionsUtil.group(list,new Transformer<User, String>(){
 
     @Override
     public String transform(User user){
         //提取名字 的姓
         return user.getName().substring(0, 1);
     }
 });
 
 LOGGER.debug(JsonUtil.format(map));
 
 

返回:

    {
        "马":[{
                "age": 55,
                "name": "马腾",
            },{
                "age": 28,
                "name": "马超",
            },{
                "age": 27,
                "name": "马岱",
            },{
                "age": 25,
                "name": "马休",
            }
        ],
        "张": [{
            "age": 28,
            "name": "张飞",
        }],
        "刘": [{
            "age": 32,
            "name": "刘备",
        }],
        "关": [{
                "age": 50,
                "name": "关羽",
            },{
                "age": 32,
                "name": "关平",
            },{
                "age": 31,
                "name": "关索",
            },{
                "age": 18,
                "name": "关兴",
            }
        ]
    }
 

Type Parameters:

T - the generic type

O - the generic type

Parameters:

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

keyTransformer - 返回的map,key转换器

Returns:

如果 beanIterable 是null或者empty,返回 Collections.emptyMap()
如果 keyTransformer 是null,抛出 NullPointerException

Since:

1.8.8

See Also:

List to Map 实现类似矩阵的逻辑 by ananbeike

group

public static <T,O> Map<T,List<O>> group(Iterable<O> beanIterable,
                         Predicate<O> includePredicate,
                         Transformer<O,T> keyTransformer)

循环 beanIterable,找到符合条件的 includePredicate的元素,将元素使用keyTransformer转成key ,相同值的元素组成list作为value,封装成map返回.

说明:

1. 返回的LinkedHashMap,key是 beanIterable中的元素 使用keyTransformer转换的值,value是 beanIterable中的元素对象(相同key值,组成list);
2. 返回的LinkedHashMap顺序,是 beanIterable 元素顺序,如果需要排序,可自行调用 SortUtil.sortMapByKeyAsc(Map), SortUtil.sortMapByKeyDesc(Map), SortUtil.sortMapByValueAsc(Map), SortUtil.sortMapByValueDesc(Map)或者, SortUtil.sortMap(Map, java.util.Comparator)

示例:

场景: 从user list中,提取 年龄 大于20的user,user的姓名的姓为key,user组成list,返回map

 
 User mateng55 = new User("马腾", 55);
 User machao28 = new User("马超", 28);
 User madai27 = new User("马岱", 27);
 User maxiu25 = new User("马休", 25);
 User zhangfei28 = new User("张飞", 28);
 User liubei32 = new User("刘备", 32);
 User guanyu50 = new User("关羽", 50);
 User guanping32 = new User("关平", 32);
 User guansuo31 = new User("关索", 31);
 User guanxing20 = new User("关兴", 18);
 
 //---------------------------------------------------------------
 List<User> list = toList(mateng55, machao28, madai27, maxiu25, zhangfei28, liubei32, guanyu50, guanping32, guansuo31, guanxing20);
 
 //---------------------------------------------------------------
 
 Predicate<User> comparatorPredicate = BeanPredicateUtil.comparatorPredicate("age", 20, Criterion.LESS);
 Map<String, List<User>> map = CollectionsUtil.group(list, comparatorPredicate, new Transformer<User, String>(){
 
     @Override
     public String transform(User user){
         //提取名字 的姓
         return user.getName().substring(0, 1);
     }
 });
 
 LOGGER.debug(JsonUtil.format(map));
 
 

返回:

    {
            "马":[{
                    "age": 55,
                    "name": "马腾",
                },{
                    "age": 28,
                    "name": "马超",
                },{
                    "age": 27,
                    "name": "马岱",
                },{
                    "age": 25,
                    "name": "马休"
                }],
            "张": [{
                "age": 28,
                "name": "张飞"
            }],
            "刘": [{
                "age": 32,
                "name": "刘备"
            }],
            "关": [{
                    "age": 50,
                    "name": "关羽"
                },{
                    "age": 32,
                    "name": "关平"
                },{
                    "age": 31,
                    "name": "关索"
                }]
        }
 

Type Parameters:

T - the generic type

O - the generic type

Parameters:

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

includePredicate - the include predicate

keyTransformer - 返回的map,key转换器

Returns:

如果 beanIterable 是null或者empty,返回 Collections.emptyMap()
如果 keyTransformer 是null,抛出 NullPointerException
如果 includePredicate 是null,那么以所有的元素进行分组
如果没有任何element match includePredicate,返回 empty LinkedHashMap

Since:

1.8.8

See Also:

Transformer.transform(Object), List to Map 实现类似矩阵的逻辑 by ananbeike

groupOne

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

循环 iterable,以元素的 propertyName属性值为key,元素为value,封装成map返回(map只put第一个匹配的元素,后面出现相同的元素将会忽略).

说明:

1. 返回的LinkedHashMap,key是 iterable中的元素对象中 propertyName的值,value是 beanIterable中的元素对象;
2. 顺序是 beanIterable propertyName的值 顺序,如果需要排序,可自行调用 SortUtil.sortMapByKeyAsc(Map), SortUtil.sortMapByKeyDesc(Map), SortUtil.sortMapByValueAsc(Map), SortUtil.sortMapByValueDesc(Map)或者, SortUtil.sortMap(Map, java.util.Comparator)
3. 间接的可以做到基于某个属性值去重的效果
4. 如果value需要是集合的话,可以调用 group(Iterable, String)方法

示例:

 List<User> list = new ArrayList<>();
 list.add(new User("张飞", 23));
 list.add(new User("刘备", 25));
 list.add(new User("刘备", 30));
 
 Map<String, User> map = CollectionsUtil.groupOne(list, "name");
 LOGGER.info(JsonUtil.format(map));
 

返回:

 {
        "张飞":         {
            "age": 23,
            "name": "张飞"
        },
        "刘备":         {
            "age": 25,
            "name": "刘备"
        }
    }
 

Type Parameters:

T - the generic type

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 Collections.emptyMap()
如果 propertyName 是null,抛出 NullPointerException
如果 propertyName 是blank,抛出 IllegalArgumentException

Since:

1.0.8

See Also:

group(Iterable, String)

newArrayList

public static <E> ArrayList<E> newArrayList()

创建 a mutable, empty ArrayList instance .

Type Parameters:

E - the element type

Returns:

the array list

Since:

1.10.7

newLinkedList

public static <E> LinkedList<E> newLinkedList()

创建 a mutable, empty LinkedList instance .

Type Parameters:

E - the element type

Returns:

the linked list

Since:

1.10.7

newCopyOnWriteArrayList

public static <E> CopyOnWriteArrayList<E> newCopyOnWriteArrayList()

创建 a mutable, empty CopyOnWriteArrayList instance .

Type Parameters:

E - the element type

Returns:

a new, empty CopyOnWriteArrayList

Since:

1.10.7

newHashSet

public static <E> HashSet<E> newHashSet()

创建 a mutable, empty newHashSet instance .

Type Parameters:

E - the element type

Returns:

the hash set

Since:

1.10.7

newLinkedHashSet

public static <E> LinkedHashSet<E> newLinkedHashSet()

创建 a mutable, empty LinkedHashSet instance .

Type Parameters:

E - the element type

Returns:

a new, empty LinkedHashSet

Since:

1.10.7