Java8 Stream流根据多个字段去重
作者：某科学的南条
这篇文章主要介绍了Java8 Stream流根据多个字段去重，具有很好的参考价值，希望对大家有所帮助。如有错误或未考虑完全的地方，望不吝赐教
Stream流根据多个字段去重
分组
list.stream().collect(Collectors.groupingBy(ClassEntity::getGrade));
java8有一个collectingAndThen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<String> 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<User> 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<String, Integer> conver = new HashMap();
users.stream().forEach(x -> {
String cKey = x.getId()+"_"+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<String, Integer> entry:conver.entrySet()){
System.out.println("key:"+entry.getKey()+","+"value:"+entry.getValue());
}
}
}运行结果如下：
以上为个人经验，希望能给大家一个参考，也希望大家多多支持脚本之家。