英文:
Java 8 Hashmap | Lombok @Data | Method not readable in Collectors.groupingBy | Composite Key
问题
以下是使用Lombok的@Data注解的bean示例：
@Data
public class XxedgeCrtV implements Serializable {
private static final long serialVersionUID = 1L;
private String registryId;
private String personPartyId;
private String source;
private String compositeKey() {
return registryId + personPartyId + source;
}
}
当我尝试在复合键上使用Java 8创建哈希映射时，它不会读取该方法：
Set<String> duplicates = xxedgeCrtVList.stream()
.collect(Collectors.groupingBy(XxedgeCrtV::compositeKey, Collectors.counting()))
.entrySet().stream()
.filter(e -> e.getValue() > 1L)
.map(e -> e.getKey())
.collect(Collectors.toSet());
有人可以建议如何让代码读取这个方法吗？
我正在将复合键作为键，因为我必须在列表中搜索重复项。
英文:
The following is a bean in use having lombok @Data annotation:
@Data
public class XxedgeCrtV implements Serializable {
private static final long serialVersionUID = 1L;
private String registryId;
private String personPartyId;
private String source;
private String compositeKey() {
return registryId + personPartyId + source;
}
}
When I tried to use create hashmap using Java 8 on composite key then it does not read the method:
Set<String> duplicates = xxedgeCrtVList.stream()
.collect(Collectors.groupingBy(XxedgeCrtV::compositeKey, Collectors.counting()))
.entrySet().stream()
.filter(e -> e.getValue() > 1L)
.map(e -> e.getKey())
.collect(Collectors.toSet());
Can anyone suggest how to get code read this method?
I am making key of composite keys as I have to search for duplicates in list.
答案1
得分: 0
以下是翻译后的内容：
方法引用和 Lombok 插件都没有错误。分组的返回类型是一个 Map：
Map<String, Long> duplicates = xxedgeCrtVList.stream()
.collect(Collectors.groupingBy(XxedgeCrtV::compositeKey, Collectors.counting()));
使用这段代码，我没有获得编译错误。
我认为这是 IDE 的问题，应该对返回类型提出警告，而不是对方法引用提出警告。可能还有其他问题：
- 如果
XxedgeCrtV是内部类，应该声明为static。 - 如果
XxedgeCrtV在不同的文件中，compositeKey的可见性不应为private。
英文:
There is neither an error in the method reference nor the Lombok plugin. The return type of grouping is a Map:
Map<String, Long> duplicates = xxedgeCrtVList.stream()
.collect(Collectors.groupingBy(XxedgeCrtV::compositeKey, Collectors.counting()));
With this code, I get no compilation error.
I bet this is the IDE issue that should complain about the return type rather than the method reference. There might be also different issue, if so:
- The class
XxedgeCrtVif inner shall bestatic. - The visibility of the
compositeKeyshould not beprivateifXxedgeCrtVis in a different file.
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