Java Lambda in Intellij: Expected not null but the lambda body is not value-compatible

Question

Trying to filter a collection using a stream, and trying to pass the following lambda to filter() a Set, which gives the arcane error in the title:

unmatchedIncomingFields.stream().filter(s-> s.matches(fieldMatchPattern))

Meanwhile, creating a Predicate object works:

unmatchedIncomingFields.stream().filter(new Predicate<String>() {
    @Override
    public boolean test(String s) {
        return s.matches(fieldMatchPattern);
    }
});

According to the JLS, a lambda body is "value-compatible" if every control path returns a value. matches() always gets called and always returns a boolean, so I don't understand what the problem is.

I've also tried all kinds of variations of the same lambda- with and without parentheses and argument types and using expression and block-with-return bodies.

Can you include a small reproductible example, and also the compiler version you are using? — Alexis C.
– Alexis C., Commented Apr 25, 2016 at 7:23
@AlexisC. The compiler is 1.8.0_77. I'm working on getting a demonstration. — ThisIsNoZaku
– ThisIsNoZaku, Commented Apr 25, 2016 at 7:56
what's the generic type of the elements in the Set, is it Set<String> or just Set? — Gerald Mücke
– Gerald Mücke, Commented Apr 25, 2016 at 8:11

ThisIsNoZaku · Accepted Answer · 2017-06-28 21:01:27Z

9

The issue looks to be incorrect, or at least somewhat misleading, error highlighting within IntelliJ, confusing where the actual error was.

The filter occurs within another lambda for a map() operation which I had not specified a return for yet, and for some reason, IntelliJ highlights the inner lambda for the filter, making it look like it is the one with the error.

edited Jun 28, 2017 at 21:01

answered Apr 25, 2016 at 8:47

ThisIsNoZaku

2,4512 gold badges28 silver badges40 bronze badges

Sign up to request clarification or add additional context in comments.

2 Comments

Marcin Over a year ago

Correct, similar thing has just happened to me. Thank you!

Visionary Software Solutions Over a year ago

This looks like an actual bug in Intellij, as the same thing just happened to me. Have we filed an issue yet?

Collectives™ on Stack Overflow

Java Lambda in Intellij: Expected not null but the lambda body is not value-compatible

1 Answer 1

2 Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

1 Answer 1

2 Comments

Your Answer

Sign up or log in

Post as a guest

Related