问题:

When I use the Java 8 method reference double colon operator (::) with new operator (e.g. MyType::new), I get this error in Eclipse of Spring Tool suite (STS):

The type org.eclipse.jdt.annotation.NonNull cannot be resolved. It is indirectly referenced from required .class files

How to get rid of this error?

回答1:

Error description is provided in Stephan Herrmann's comment. There is open Eclipse issue to make this issue more user friendly.

Solution is to include following dependency:

<dependency>
    <groupId>org.eclipse.jdt</groupId>
    <artifactId>org.eclipse.jdt.annotation</artifactId>
    <version>2.0.0</version>
</dependency>

回答2:

Eclipse has a feature called annotation-based null analysis, which provides compile-time checks using annotations (e.g. @NonNull or @Nullable). You get this error when annotations are missing in the classpath.

If you don't plan to use the annotation-based null analysis feature, you can just disable it in Eclipse.

Open the global or project settings and go to Java > Compiler > Warnings. In the Null analysis category, uncheck Enable annotation-based null analysis. Then rebuild the workspace and those errors won't show again.