使用流过滤POJO列表-无法强制转换ClassCastException java.util.LinkedHashMap

Question

As familiar as the question is, my problem is a little odd.

This is the POJO I have:

public class POJO implements Serializable {
    @JsonProperty("ID")
    private UUID id;

    @JsonProperty("Name")
    private String name;

    // getters and setters
}

I am trying to filter a list of this POJO using the following piece of code:

List<POJO> pojoList = getListOfPojosFromSomeMethod();
List<POJO> filteredPOJO = pojoList.stream()
                          .filter(p -> p.getName().equals("POJOName"))
                          .collect(Collectors.toList())

I am unable to filter the list. I get the following exception:

java.lang.ClassCastException: java.util.LinkedHashMap cannot be cast to com.models.POJO
at java.util.stream.ReferencePipeline$2$1.accept(ReferencePipeline.java:174)
at java.util.ArrayList$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)

I tried to use map as well:

List<POJO> pojoList = getListOfPojosFromSomeMethod();
List<POJO> filteredPOJO = pojoList.stream()
                          .filter(p -> p.getName().equals("POJOName")
                          .map(p -> new POJO(p))
                          .collect(Collectors.toList());

Same exception. No change whatsoever. I read somewhere that the exception is because of Jackson serialization.

How do I filter lists using streams and Jackson at the same time? I am unable to find a solution.

Thanks in advance.

Answer 1

You can try :

Predicate<POJO> filterPredicate = item -> "POJOName".equals(item.getName());

List<POJO> filteredPOJOs = pojoList.stream()
                      .filter(filterPredicate)
                      .collect(Collectors.toList())

Answer 2

There is no problem in the first example :

    List<POJO> filteredPOJO = pojoList.stream()
                      .filter(p -> p.getName().equals("POJOName"))
                      .collect(Collectors.toList());

I just noticed that a parenthesis is missing after : equals("POJOName") to close filter params.