最近碰到一个问题，自定义数据类型列表中出现了重复数据，需要去重。处理去重的办法很多，比如借助Set集合类，使用双重循环拿每一个元素和其他元素对比等。这里介绍一种简单而且比较优雅的方式：使用Rxjava2中的distinct操作符来实现。

       网上介绍这种方式的文章非常多，但基本上都是拿整数类型数据来演示，比如：

1 Observable.just(1, 1, 2, 2, 3, 4).distinct().subscribe(new Consumer<Integer>() {
2             @Override
3             public void accept(Integer integer) throws Exception {
4                 Log.d(TAG, "[distinct-accept]integer = " + integer);
5             }
6         });

但实际工作中碰到的数据类型却是自定义类型，看到上述代码后本人还是有时有点手足无措，没法直接拿到依葫芦画瓢。后来自己研究了一下，在上述代码基础上转了一个弯，解决了这个问题，下面记录一下。

使用的自定义类型为：

 1 public class UserInfo {
 2     private String userId;
 3     private String userName;
 4 
 5     public UserInfo(String userId, String userName) {
 6         this.userId = userId;
 7         this.userName = userName;
 8     }
 9 
10     public String getUserId() {
11         return userId;
12     }
13 
14     public void setUserId(String userId) {
15         this.userId = userId;
16     }
17 
18     public String getUserName() {
19         return userName;
20     }
21 
22     public void setUserName(String userName) {
23         this.userName = userName;
24     }
25 
26     @Override
27     public boolean equals(Object o) {
28         if (this == o) return true;
29         if (o == null || getClass() != o.getClass()) return false;
30         UserInfo userInfo = (UserInfo) o;
31         return Objects.equals(userId, userInfo.userId);
32     }
33 
34     @Override
35     public int hashCode() {
36         return Objects.hash(userId);
37     }
38 
39     @Override
40     public String toString() {
41         return "UserInfo{" +
42                 "userId='" + userId + '\'' +
43                 ", userName='" + userName + '\'' +
44                 '}';
45     }
46 }

测试代码为

 1 private void testDistinct() {
 2     List<UserInfo> userInfoList = new ArrayList<>();
 3     userInfoList.add(new UserInfo("id-0", "name-0"));
 4     for (int i = 0; i < 10; i++) {
 5         userInfoList.add(new UserInfo("id-" + i, "name-" + i));
 6     }
 7     Log.d(TAG, "[testDistinct]去重前");
 8     for (UserInfo userInfo : userInfoList) {
 9         Log.d(TAG, "[testDistinct]userInfo = " + userInfo.toString());
10     }
11     Log.d(TAG, "[testDistinct]去重后");
12     Observable.fromIterable(userInfoList).distinct().subscribe(new Consumer<UserInfo>() {
13         @Override
14         public void accept(UserInfo userInfo) throws Exception {
15             Log.d(TAG, "[distinct-accept]userInfo = " + userInfo.toString());
16         }
17     });
18 }

日志

 1 2022-01-08 16:41:31.858 12668-12668/com.beantechs.rxjavademo D/rxjava_demo: [testDistinct]去重前
 2 2022-01-08 16:41:31.858 12668-12668/com.beantechs.rxjavademo D/rxjava_demo: [testDistinct]userInfo = UserInfo{userId='id-0', userName='name-0'}
 3 2022-01-08 16:41:31.858 12668-12668/com.beantechs.rxjavademo D/rxjava_demo: [testDistinct]userInfo = UserInfo{userId='id-0', userName='name-0'}
 4 2022-01-08 16:41:31.858 12668-12668/com.beantechs.rxjavademo D/rxjava_demo: [testDistinct]userInfo = UserInfo{userId='id-1', userName='name-1'}
 5 2022-01-08 16:41:31.858 12668-12668/com.beantechs.rxjavademo D/rxjava_demo: [testDistinct]userInfo = UserInfo{userId='id-2', userName='name-2'}
 6 2022-01-08 16:41:31.858 12668-12668/com.beantechs.rxjavademo D/rxjava_demo: [testDistinct]userInfo = UserInfo{userId='id-3', userName='name-3'}
 7 2022-01-08 16:41:31.858 12668-12668/com.beantechs.rxjavademo D/rxjava_demo: [testDistinct]userInfo = UserInfo{userId='id-4', userName='name-4'}
 8 2022-01-08 16:41:31.858 12668-12668/com.beantechs.rxjavademo D/rxjava_demo: [testDistinct]userInfo = UserInfo{userId='id-5', userName='name-5'}
 9 2022-01-08 16:41:31.858 12668-12668/com.beantechs.rxjavademo D/rxjava_demo: [testDistinct]userInfo = UserInfo{userId='id-6', userName='name-6'}
10 2022-01-08 16:41:31.858 12668-12668/com.beantechs.rxjavademo D/rxjava_demo: [testDistinct]userInfo = UserInfo{userId='id-7', userName='name-7'}
11 2022-01-08 16:41:31.858 12668-12668/com.beantechs.rxjavademo D/rxjava_demo: [testDistinct]userInfo = UserInfo{userId='id-8', userName='name-8'}
12 2022-01-08 16:41:31.858 12668-12668/com.beantechs.rxjavademo D/rxjava_demo: [testDistinct]userInfo = UserInfo{userId='id-9', userName='name-9'}
13 2022-01-08 16:41:31.858 12668-12668/com.beantechs.rxjavademo D/rxjava_demo: [testDistinct]去重后
14 2022-01-08 16:41:31.870 12668-12668/com.beantechs.rxjavademo D/rxjava_demo: [distinct-accept]userInfo = UserInfo{userId='id-0', userName='name-0'}
15 2022-01-08 16:41:31.871 12668-12668/com.beantechs.rxjavademo D/rxjava_demo: [distinct-accept]userInfo = UserInfo{userId='id-1', userName='name-1'}
16 2022-01-08 16:41:31.871 12668-12668/com.beantechs.rxjavademo D/rxjava_demo: [distinct-accept]userInfo = UserInfo{userId='id-2', userName='name-2'}
17 2022-01-08 16:41:31.871 12668-12668/com.beantechs.rxjavademo D/rxjava_demo: [distinct-accept]userInfo = UserInfo{userId='id-3', userName='name-3'}
18 2022-01-08 16:41:31.871 12668-12668/com.beantechs.rxjavademo D/rxjava_demo: [distinct-accept]userInfo = UserInfo{userId='id-4', userName='name-4'}
19 2022-01-08 16:41:31.871 12668-12668/com.beantechs.rxjavademo D/rxjava_demo: [distinct-accept]userInfo = UserInfo{userId='id-5', userName='name-5'}
20 2022-01-08 16:41:31.871 12668-12668/com.beantechs.rxjavademo D/rxjava_demo: [distinct-accept]userInfo = UserInfo{userId='id-6', userName='name-6'}
21 2022-01-08 16:41:31.871 12668-12668/com.beantechs.rxjavademo D/rxjava_demo: [distinct-accept]userInfo = UserInfo{userId='id-7', userName='name-7'}
22 2022-01-08 16:41:31.871 12668-12668/com.beantechs.rxjavademo D/rxjava_demo: [distinct-accept]userInfo = UserInfo{userId='id-8', userName='name-8'}
23 2022-01-08 16:41:31.871 12668-12668/com.beantechs.rxjavademo D/rxjava_demo: [distinct-accept]userInfo = UserInfo{userId='id-9', userName='name-9'}

日志中红色部分显示了去重效果。

       本示例中是把具有相同userId的对象视为同一个对象，所有在UserInfo类中重写了equals()方法和hashCode()方法，这是关键点。如果判断是否为同一对象的条件有变化，就需要相应地重写equals()方法和hashCode()方法。