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javajava-stream

Java Stream throws java.lang.TypeNotPresentException

I have the following Problem. I have an array of Strings representing email addresses and i want to convert the strings to another Type. To do this i am using Java Streams.

final List<String> recipientsStrings = Arrays.asList("test@mail.com", "test2@mail.com")
final InternetAddress[] to = (InternetAddress[]) recipientsStrings
            .stream()
            .map(this::createInternetAddress)
            .toArray();

and the signature of createInternetAddress is:

private InternetAddress createInternetAddress(final String address)

The Problem is, that the map function is throwing a java.lang.TypeNotPresentException. The strange thing is, that if i write a lambda function instead of a method reference it works. So my question is what is the difference between the following pieces of code.

.map(this::createInternetAddress)

and

.map(mail -> this.createInternetAddress(mail))
Solution

  • With both signatures, I got this error:

    Exception in thread "main" java.lang.ClassCastException: class [Ljava.lang.Object; cannot be cast to class [LInternetAddress; ([Ljava.lang.Object; is in module java.base of loader 'bootstrap'; [LInternetAddress; is in unnamed module of loader 'app')

    Either lambda function or method reference is equivalent, your issue is with the casting (InternetAddress[]), to solve this you can simply use:

    final InternetAddress[] to = recipientsStrings
        .stream()
        .map(this::createInternetAddress)
        .toArray(InternetAddress[]::new);