Java8 Stream流根据多个字段去重

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

list.stream()

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

List<String> classNameList = new ArrayList( new HashSet(list));

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;

     }

}

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());

         }

     }

}