Java8 Stream流根据多个字段去重

Java8 Stream流根据多个字段去重

目录Stream流根据多个字段去重Stream多字段去重,去重求和完整demo如下启动主函数

Stream流根据多个字段去重

分组

list.stream().collect(Collectors.groupingBy(ClassEntity::getGrade));

java8有一个collectingAndTtOroWhen可以根据多个字段去重

list.stream()

.collect(Collectors.collectingAndThen(Collectors.toCollection(() -> new TreeSet<>(Comparator.comparing(o -> o.getProfessionId() + ";" + o.getGrade()))), ArrayList::new));

通过hashSet去重：

该种去重是bean完全相同的时候算重复数据

List classNameList = new ArrayList(new HashSet(list));

Stream多字段去重,去重求和

stream进行list的循环遍历。

conver的String由去重条件组成，中间用下划线或特殊字符分割

代码如下：

完整demo如下

附带测试结果

class User {

private int id;

private String name;

private Integer record;

public User() {

}

public User(int id,String name, Integer record) {

}

public int getId() {

return id;

}

public void setId(int id) {

this.id = id;

}

public String getName() {

return name;

}

public void setName(String name) {

this.name = name;

}

public Integer getRecord() {

return record;

}

public void setRecord(Integer record) {

this.record = record;

}

}

启动主函数

public class Main {

public static void main(String[] args) {

List users = new ArrayList<>();

User user1 = new User();

user1.setId(1);

user1.setName("小明");

user1.setRecord(50);

users.add(user1);

User user2 = new User();

user2.setId(1);

user2.setName("小明");

user2.setRecord(60);

users.add(user2);

User user3 = new User();

user3.setId(2);

user3.setName("小华");

user3.setRecord(70);

users.add(user3);

User user4 = new User();

user4.setId(2);

user4.setName("小华");

user4.setRecord(80);

users.add(user4);

User user5 = new User();

user5.setId(3);

user5.setName("小芳");

user5.setRecord(100);

users.add(user5);

Map conver = new HashMap();

users.stream().forEach(x -> {

String cKey = x.getId()http://+"_"+x.getName();

if (!conver.containsKey(cKey)) {

conver.put(cKey, x.getRecord());

} else {

Integer temp = conver.get(cKey);

conver.put(cKey, (null == temp ? 0 : temp) + (null == x.getRecord() ? 0 : x.getRecord()));

}

});

System.out.println(conver.size());

for(Map.Entry entry:conver.entrySet()){

System.out.println("key:"+entry.getKey()+","+"value:"+entry.getValue());

}

}

}

运行结果如下：

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