阿泽Anza

最近需要用到对一个对象集合序列去重，而且去重是根据这个对象里面的两个字段，以下是代码可供参考，其实很简单，通过重写实体的hashCode和equals即可实现，jdk1.8之后set的底层实现方式也是通过hashMap，所以采用此方法来处理即可，备注留用！

    @Override
    public boolean equals(Object obj) {
        if (this == obj)
            return true;
        if (obj == null)
            return false;
        if (getClass() != obj.getClass())
            return false;

        if (obj instanceof HttpMtInfo) {
            HttpMtInfo other = (HttpMtInfo) obj;
            if (content == null) {
                if (other.content != null)
                    return false;
            } else if (!content.equals(other.content))
                return false;
            if (destid == null) {
                if (other.destid != null)
                    return false;
            } else if (!destid.equals(other.destid))
                return false;

            // 比较每个属性的值 一致时才返回true
            if (other.content.equals(this.content) && other.destid.equals(this.destid))
                return true;
        }
        return true;
    }

    /**
     * 重写hashcode 方法，返回的hashCode不一样才再去比较每个属性的值
     */
    @Override
    public int hashCode() {
        return content.hashCode() * destid.hashCode();
    }

测试代码：

    public static void main(String[] args) {
        HttpMtInfo httpMtInfo = new HttpMtInfo();
        httpMtInfo.setUsercode("wkl");
        httpMtInfo.setPassword("324");
        httpMtInfo.setMsgid("dafasdfasdfads");
        httpMtInfo.setContent("测试1");
        httpMtInfo.setDestid("15210086628");

        HttpMtInfo httpMtInfo1 = new HttpMtInfo();
        httpMtInfo1.setUsercode("wklds");
        httpMtInfo1.setPassword("324");
        httpMtInfo1.setMsgid("dafasdfasdfads");
        httpMtInfo1.setContent("测试2");
        httpMtInfo1.setDestid("15210086628");

        HttpMtInfo httpMtInfo2 = new HttpMtInfo();
        httpMtInfo2.setUsercode("wklds");
        httpMtInfo2.setPassword("324");
        httpMtInfo2.setMsgid("dafasdfasdfads");
        httpMtInfo2.setContent("测试3");
        httpMtInfo2.setDestid("18401555228");

        HttpMtInfo httpMtInfo3 = new HttpMtInfo();
        httpMtInfo3.setUsercode("wklds");
        httpMtInfo3.setPassword("324");
        httpMtInfo3.setMsgid("dafasdfasdfads");
        httpMtInfo3.setContent("测试3");
        httpMtInfo3.setDestid("18401555228");

        HttpMtInfo httpMtInfo4 = new HttpMtInfo();
        httpMtInfo4.setUsercode("wklds");
        httpMtInfo4.setPassword("324");
        httpMtInfo4.setMsgid("dafasdfasdfads");
        httpMtInfo4.setContent("测试5");
        httpMtInfo4.setDestid("18401553228");

        Set<HttpMtInfo> sets = new HashSet<>();
        sets.add(httpMtInfo);
        sets.add(httpMtInfo1);
        sets.add(httpMtInfo2);
        sets.add(httpMtInfo3);
        sets.add(httpMtInfo4);

        for (HttpMtInfo item : sets) {
            System.out.println(item.toString());
        }
    }

输出结果：

HttpMtInfo [msgid=dafasdfasdfads, servicecodeadd=null, destid=18401553228, datacode=null, contentlen=null, content=测试5, usercode=wklds, password=324, serverid=null, senddate=null]
HttpMtInfo [msgid=dafasdfasdfads, servicecodeadd=null, destid=15210086628, datacode=null, contentlen=null, content=测试2, usercode=wklds, password=324, serverid=null, senddate=null]
HttpMtInfo [msgid=dafasdfasdfads, servicecodeadd=null, destid=15210086628, datacode=null, contentlen=null, content=测试1, usercode=wkl, password=324, serverid=null, senddate=null]
HttpMtInfo [msgid=dafasdfasdfads, servicecodeadd=null, destid=18401555228, datacode=null, contentlen=null, content=测试3, usercode=wklds, password=324, serverid=null, senddate=null]

顺带着从别的地方看到的：

在阿里巴巴Java开发是手册的集合处理中需要强制遵循如下规则：
1)只要重写equals，就必须重写hashCode；
2)因为Set存储的是不重复的对象，依据hashCode和equals进行判断，所以Set存储的对象必须重写这两个方法。
3)如果自定义对象做为Map的键，那么必须重写hashCode和equals。
正例：String重写了hashCode和equals方法，所以我们可以方便的使用String对象作为key来使用。