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IllegalArgumentException or NullPointerException for a null parameter? [closed]
You should be using IllegalArgumentException (IAE), not NullPointerException (NPE) for the following reasons: First, the NPE JavaDoc explicitly lists the cases where NPE is appropriate. Notice that all of them are thrown by the runtime when null is used inappropriately. In contrast, the IAE JavaDoc couldn’t be more clear: “Thrown to indicate that a method … Read more
Unity: Null while making new class instance
public class Rule : MonoBehaviour{} Rule rule2 = new Rule(); You can’t use new keyword to create new instance if you are inheriting from MonoBehaviour. You should get exception that says: You are trying to create a MonoBehaviour using the ‘new’ keyword. This is not allowed. MonoBehaviours can only be added using AddComponent(). Alternatively, your … Read more
Unable to cast object of type ‘System.DBNull’ to type ‘System.String`
With a simple generic function you can make this very easy. Just do this: return ConvertFromDBVal<string>(accountNumber); using the function: public static T ConvertFromDBVal<T>(object obj) { if (obj == null || obj == DBNull.Value) { return default(T); // returns the default value for the type } else { return (T)obj; } }
getActivity() returns null in Fragment function
commit schedules the transaction, i.e. it doesn’t happen straightaway but is scheduled as work on the main thread the next time the main thread is ready. I’d suggest adding an onAttach(Activity activity) method to your Fragment and putting a break point on it and seeing when it is called relative to your call to asd(). … Read more
Why does NULL = NULL evaluate to false in SQL server
Think of the null as “unknown” in that case (or “does not exist”). In either of those cases, you can’t say that they are equal, because you don’t know the value of either of them. So, null=null evaluates to not true (false or null, depending on your system), because you don’t know the values to … Read more
SQL is null and = null [duplicate]
In SQL, a comparison between a null value and any other value (including another null) using a comparison operator (eg =, !=, <, etc) will result in a null, which is considered as false for the purposes of a where clause (strictly speaking, it’s “not true”, rather than “false”, but the effect is the same). … Read more
Why is null an object and what’s the difference between null and undefined?
(name is undefined) You: What is name? (*) JavaScript: name? What’s a name? I don’t know what you’re talking about. You haven’t ever mentioned any name before. Are you seeing some other scripting language on the (client-)side? name = null; You: What is name? JavaScript: I don’t know. In short; undefined is where no notion … Read more
Which @NotNull Java annotation should I use?
Since JSR 305 (whose goal was to standardize @NonNull and @Nullable) has been dormant for several years, I’m afraid there is no good answer. All we can do is to find a pragmatic solution and mine is as follows: Syntax From a purely stylistic standpoint I would like to avoid any reference to IDE, framework … Read more
Not equal != operator on NULL
<> is Standard SQL-92; != is its equivalent. Both evaluate for values, which NULL is not — NULL is a placeholder to say there is the absence of a value. Which is why you can only use IS NULL/IS NOT NULL as predicates for such situations. This behavior is not specific to SQL Server. All … Read more