error: package com.android.annotations does not exist

Question

I have the following class

import com.android.annotations.NonNullByDefault;

@NonNullByDefault
public final class Log {
    ...
}

and here

Answer 1

Annotations come from the support's library which are packaged in android.support.annotation.

As another option you can use @NonNull annotation which denotes that a parameter, field or method return value can never be null.
It is imported from import android.support.annotation.NonNull;