The following code is flagged with an error by NetBeans despite that it compiles fine. The classes pasted must be in separate files, otherwise the bug will not manifest itself:

    public class MyTestContainer {
        public void setEntry(MyTestEntryFactory entryFactory) {
        }
    }

    public interface MyTestEntry {
        public <DataType> void doSomething();
    }

    public interface MyTestEntryFactory {
        public MyTestEntry create();
    }

    public class MyTest {
        public static void test() {
            MyTestContainer container = new MyTestContainer();
            container.setEntry(() -> {
                return new MyTestEntry() {
                    @Override
                    public <DataType> void doSomething() {
                    }
                };
            });
        }
    }

The line containing "container.setEntry" is flagged as an error with the message: "The type of setEntry(MyTestEntryFactory) is erroneous".

Workaround: Casting the lambda explicitly to MyTestEntryFactory solves the issue.

Another issue in this code (though it might be unrelated) that the anonymous class implementing MyTestEntry is flagged to be convertible to lambda which is not true because doSomething() has a generic argument.