无法从 Stream 转换<t>至 boolean</t>

Question

I'm trying to filter a list of objects say BOLReference based on a key which is present in the inner object of one of the List of Objects of this BOLReference.

List<BOLReference> bolRef = complianceMongoTemplate.find(findQuery, BOLReference.class);

Optional<BOLReference> bref = bolRef.stream().filter(br -> br.getWorkflowExceptions().stream()
                        .filter(bk -> bk.getBusinessKeyValues().get(businessKey)
                        .equalsIgnoreCase("ABCD1234"))).findFirst();

While doing so I'm getting error as:

Cannot convert from Stream<WorkFlowExceptions> to boolean

My BOLReference looks like below:

private String ediTransmissionId;
private List<WorkflowExceptions> workflowExceptions;

And my WorkflowExceptions looks like:

private String category;
private Map<String,String> businessKeyValues;

Answer 1

Optional<BOLReference> bref = bolRef.stream()
    .filter(br -> 
        br.getWorkflowExceptions().stream()
            .anyMatch(bk ->
                bk.getBusinessKeyValues().get(businessKey)
                    .equalsIgnoreCase("ABCD1234")))
    .findFirst();

Failing anyMatch I think.

Answer 2

A filter clause does not return a boolean but a stream. This causes a problem because your first filter expects a boolean result, but gets a stream from the second filter. You can use anyMatch instead to achieve the desired result.

You can make stream expressions more readable by formatting them on more lines and extracting complex logic into methods.

You could fix & refactor it like this:

String businessKey = null;
String targetValue = "ABCD1234";

Optional<BOLReference> bref = bolReferences.stream()
    .filter(br -> br. hasBusinessKey(businessKey, targetValue))
    .findFirst();

And:

public class BOLReference {

    // ...

    public boolean hasBusinessKey(String key, String value) {
        return getWorkflowExceptions().stream()
            .anyMatch(wfe -> wfe.hasBusinessKey(key, value));
    }
}

And:

public class WorkflowExceptions {

    // ...

    public boolean hasBusinessKey(String key, String value) {
        return getBusinessKeyValues().get(key).equalsIgnoreCase(value);
    }
}