第java8根據(jù)某一屬性過濾去重的實例目錄java8根據(jù)某一屬性過濾去重根據(jù)list某一屬性去重過濾StudentExamState=0的數(shù)據(jù)過濾ExamRoomStudentCount=0的數(shù)據(jù)Java8stream根據(jù)對象字段去重stream對list中的對象進(jìn)行去重

java8根據(jù)某一屬性過濾去重

最近小編剛接觸到j(luò)ava8特性，在不知道有java8特性的時候，一個for循環(huán)套一個for循環(huán)，自從接觸大java8，為自己省了很多事，節(jié)省了很多代碼量.

根據(jù)list某一屬性去重

//根據(jù)id去重

examRoomModelLists=examRoomModelLists.stream().collect(Collectors.collectingAndThen(Collectors.toCollection(

//利用TreeSet的排序去重構(gòu)造函數(shù)來達(dá)到去重元素的目的

//根據(jù)firstName去重

()-newTreeSet(Cparing(ExamRoomModel::getId))),ArrayList::new));

過濾StudentExamState=0的數(shù)據(jù)

em.setNoLoginExamineeCount((examinee.stream().map(ExamineeEntity::getStudentExamState).filter(x-

x==0).collect(Collectors.toList())).size());

}

過濾ExamRoomStudentCount=0的數(shù)據(jù)

ListExamRoomModelfilterList=examRoomModelLists.stream().filter(ExamRoomModel-

!Objects.equals(ExamRoomModel.getExamRoomStudentCount(),0)).collect(Collectors.toList());

是不是很方便，換成以前過濾去重不知道要寫多少橫代碼，現(xiàn)在一行解決.

Java8stream根據(jù)對象字段去重

publicclassJava8StreamTest{

publicstaticclassBook{

privateStringid;

privateStringname;

publicBook(Stringid,Stringname){

this.id=id;

=name;

publicStringgetId(){

returnid;

publicvoidsetId(Stringid){

this.id=id;

publicStringgetName(){

returnname;

publicvoidsetName(Stringname){

=name;

@Override

publicStringtoString(){

return"Book{"+

"id='"+id+'\''+

",name='"+name+'''+

'}';

@Test

publicvoidtestUnique(){

ListBookbooks=Lists.newArrayList(newBook("1","1"),newBook("2","2"),newBook("3","3"),newBook("2","2"));

//使用TreeSet去重

ListBookunique1=books.stream().collect(

collectingAndThen(toCollection(()-newTreeSet(Cparing(o-o.getId()))),

ArrayList::new));

System.out.println(unique1);

//使用map去重

ListBookunique2=books.stream()

.filter(distinctByKey(o-o.getId()))

.collect(Collectors.toList());

System.out.println(unique2);

publicstaticTPredicateTdistinctByKey(FunctionsuperT,ObjectkeyExtractor){

MapObject,Booleanseen=newConcurrentHashMap();

System.out.println("這個函數(shù)將應(yīng)用到每一個item");

returnt-seen.putIfAbsent(keyExtractor.apply(t),Boolean.TRUE)==null;

stream對list中的對象進(jìn)行去重

首先我們有一個對象屬性如下

@Data

publicclassPerson{

privateStringid;

privateStringname;

privateStringsex;

}

我們根據(jù)屬性name來去重，去重代碼如下

ListPersonpersons=newArrayList();

//賦值初始化過程省略

ListPersonuniqueByName=persons.stream().collect(

Collectors.collectingAndThen(

Collectors.toCollection(()-newTreeSet(Cparing(Person::getName))),ArrayList::new)

);

根據(jù)name,sex兩個屬性去重

ListPersonpersons=newArrayList();

//賦值初始化過程省略

ListPersonuniqueByNameAndSex=persons.stream().collect(

Collectors.collectingAndThen(