Java Peek 中的 8 个条件逻辑？

Question

我目前有一些 Java 8 代码，看起来像这样 - 很确定我可以将它组合成一个调用，但不确定如何在 Looped 映射中进行条件调用。可以用 peek() 做到这一点吗？还是其他Java8调用？

当前代码

//turn above groups into a map, grouped by Resolution
Map<Long,List<LeadChannel>> mappedUp = groups
                .stream()
                .collect( Collectors.groupingBy( channel->channel.getResolution().getId() ) );

下一位根据Key的ID手动转换为String的Map。

Map<String, List<LeadChannel>> finalMap = new HashMap<String, List<LeadChannel>>();

for ( Map.Entry<Long,List<LeadChannel>> entry : mappedUp.entrySet()) {
    if(  !entry.getKey().equals( RESOLVED_STATUS ) ) {
        finalMap.put( "unresolved", entry.getValue() );
    } else {
        finalMap.put( "resolved", entry.getValue() );
    }
}

我正在尝试这样做：

 Map<String,List<LeadChannel>> mappedUp = groups
                        .stream()
                        .collect( Collectors.groupingBy( channel->channel.getResolution().getId() ) )
.entrySet()
.stream()
.peek( if statement etc.. )

Answer 1

您似乎要找的是一个有条件的 groupingBy 作为：

Map<String, List<LeadChannel>> finalMap = groups
        .stream()
        .collect(Collectors.groupingBy(channel ->
                channel.getResolution().getId().equals(RESOLVED_STATUS) ?
                        "unresolved" : "resolved"));

或者在多个管道中，了解如何对数据进行分区，然后根据问题中共享的条件进一步映射：

Map<Boolean, List<LeadChannel>> mappedUp = groups
        .stream()
        .collect(Collectors.partitioningBy(channel -> 
                channel.getResolution().getId().equals(RESOLVED_STATUS)));

Map<String, List<LeadChannel>> finalMap = mappedUp.entrySet().stream()
        // in a similar manner you can map your current map's entries as well
        .map(e -> new AbstractMap.SimpleEntry<>(e.getKey() ? "resolved" : "unresolved", e.getValue())) 
        .collect(Collectors.toMap(Map.Entry::getKey, Map.Entry::getValue));

或者按照 Holger 的建议，最好使用 lambda 直接收集为

Map<String, List<LeadChannel>> finalMap = mappedUp.entrySet().stream()
        .collect(Collectors.toMap(e -> e.getKey()? "resolved": "unresolved", Map.Entry::getValue))

Java Peek 中的 8 个条件逻辑？

Java 8 conditional logic inside Peek?

java

lambda

java-8

java-stream

collectors