Java 8 List 到 Map 覆盖重复键

Question

这个问题已经有答案了:

Ignore duplicates when producing map using streams (12 个回答)

已关闭 6 年前。

您好，我在执行代码时遇到错误:

java.lang.IllegalStateException: Duplicate key ad.ecs.core.scriptengine.SiteIDAndNPI@3a75ce6f
at java.util.stream.Collectors.lambda$throwingMerger$0(Collectors.java:133)
at java.util.HashMap.merge(HashMap.java:1253)
at java.util.stream.Collectors.lambda$toMap$58(Collectors.java:1320)
at java.util.stream.ReduceOps$3ReducingSink.accept(ReduceOps.java:169)
at java.util.ArrayList$ArrayListSpliterator.forEachRemaining(ArrayList.java:1374)
at java.util.stream.AbstractPipeline.copyInto(AbstractPipeline.java:481)
at java.util.stream.AbstractPipeline.wrapAndCopyInto(AbstractPipeline.java:471)
at java.util.stream.ReduceOps$ReduceOp.evaluateSequential(ReduceOps.java:708)
at java.util.stream.AbstractPipeline.evaluate(AbstractPipeline.java:234)
at java.util.stream.ReferencePipeline.collect(ReferencePipeline.java:499)
at ad.ecs.core.scriptengine.Utils.getInterfaceIDsWithSiteIDAndNPI(Utils.java:689)

我正在尝试将我的列表分组到 map 中:

public static Map<Integer, SiteIDAndNPI> getInterfaceIDsWithSiteIDAndNPI(Session session) {
    @SuppressWarnings("unchecked")
    List<Srvsetup> srvsetups = session.createCriteria(Srvsetup.class)
            .add(Restrictions.gt("scriptinterfaceid", 0))
            .list(); 
    Map<Integer, SiteIDAndNPI> interfaceIDs = srvsetups.stream()
            .collect(Collectors.toMap(srv -> srv.getScriptinterfaceid(), 
                    srv -> getSiteIDAndNPI(srv.getId().getSiteid(), session)));

    @SuppressWarnings("unchecked")
    List<Facsetup> facsetups = session.createCriteria(Facsetup.class)
            .add(Restrictions.gt("scriptinterfaceid", 0))
            .list(); 
    interfaceIDs.putAll(facsetups.stream()
            .collect(Collectors.toMap(fac -> fac.getScriptinterfaceid(), 
                    fac -> getSiteIDAndNPI(fac.getPlid(), session))));
    return interfaceIDs;
}

public static SiteIDAndNPI getSiteIDAndNPI(int siteID, Session session) {
    SiteIDAndNPI siteIDAndNPI = new SiteIDAndNPI();
    siteIDAndNPI.setSiteID(siteID);
    Mdsetup1 mdsetup1 = (Mdsetup1) session.get(Mdsetup1.class, siteID);
    if (mdsetup1 != null) 
        siteIDAndNPI.setNPI(mdsetup1.getProviderId());
    return siteIDAndNPI;
}

我查看了此链接:Java 8 List<V> into Map<K, V>

有人建议使用分组依据。但我不想得到这样的 map :

Map<Integer, List<SiteIDAndNPI>>

相反，我想覆盖重复的键。不做一些丑陋的代码就可以实现吗？

Answer 1

当然。只需使用 toMap 重载接受合并函数:

 Collectors.toMap(fac -> fac.getScriptinterfaceid(), 
                fac -> getSiteIDAndNPI(fac.getPlid(), session, log),
                (value1, value2) -> value2 /* accept the second version */))