使用@NonNullByDefault和数组时，如何删除“空注是多余的”警告？ （Eclipse，NullAnnotation）

Question

I get the error

Null type safety (type annotations): The expression of type 'String' needs unchecked conversion to conform to '@NonNull String'

at statement A of this class:

package org.abego.util;

public class MyClass {
    private String[] names = new String[]{"Alice", "Bob", "Charlie"};

    public String getName(int index) {
        String name = names[index];
        return name; /* statement A */
    }
}

The package org.abego.util defines the default nullness to be "@NonNull":

@org.eclipse.jdt.annotation.NonNullByDefault
package org.abego.util;

When adding @NonNull to the array definition:

package org.abego.util;

import org.eclipse.jdt.annotation.NonNull;

public class MyClass {
    private @NonNull String[] names = new @NonNull String[]{"Alice", "Bob", "Charlie"};

    public String getName(int index) {
        String name = names[index];
        return name; /* statement A */
    }
}

the warning at statement A goes away, however I get a new warning

The nullness annotation is redundant with a default that applies to this location

for the type @NonNull String[] in the array definition.

I found no way to make this code warning-free.

Could the 'redundant' warning be wrong? It is my understanding the NonNullByDefault declaration will make sure a type definition String[] will be interpreted as String @NonNull[] , but not as @NonNull String[] or as @NonNull String @NonNull[] . So the explicit nullness annotation in @NonNull String[] is not redundant, but necessary to get the effective type @NonNull String @NonNull[] .

(I am using Eclipse 4.5 (Mars) and jdk1.8.0_60.)

Answer 1

Your expectations are correct. @NonNullBeDefault doesn't affect any details of an array type (unless you include DefaultLocation.ARRAY_CONTENTS in the annotation's value ).

I believe this to be a variant of https://bugs.eclipse.org/440398

Thanks for the concise example, btw.