As further comment, you should be aware of this term in the equals contract: From Object.equals(Object): For any non-null reference value x, x.equals(null) should return false. The way to compare with null is to use x == null and x != null. Moreover, x.field and x.method() throws NullPointerException if x == null.
If you just want to check whether there’s a truthy value, you can do: If you need to check specifically for an empty string over null, I would think checking against “” is your best bet, using the === operator (so that you know that it is, in fact, a string you’re comparing against).
nil is the literal null value for Objective-C objects, corresponding to the abstract type id or any Objective-C type declared via @interface. For instance: Nil is the literal null value for Objective-C classes, corresponding to the type Class. Since most code doesn’t need variables to reference classes, its use is not common. One example is: NULL is the literal null value for … Read more
The language specification is where null is defined, and it says There is also a special null type, the type of the expression null, which has no name. Because the null type has no name, it is impossible to declare a variable of the null type or to cast to the null type. The null … Read more
On the actual behavior, there is no difference. They all return None and that’s it. However, there is a time and place for all of these. The following instructions are basically how the different methods should be used (or at least how I was taught they should be used), but they are not absolute rules so you … Read more
The chunk vector ceases to exist at the end of the for loop body. It’s still referenced by some thread. That’s called a dangling reference, and it’s not good. The error that you see may however be related to Result. Its definition isn’t provided (at the time of writing this answer) so it’s difficult to say. Remember that as the one … Read more
The language specification is where null is defined, and it says There is also a special null type, the type of the expression null, which has no name. Because the null type has no name, it is impossible to declare a variable of the null type or to cast to the null type. The null … Read more
It’s not data that is null, but dataList. You need to create one with Even better: since it’s a field, make it private. And if there’s nothing preventing you, make it also readonly. Just good practice. Aside The correct way to check for nullity is if(data != null). This kind of check is ubiquitous for reference types; even Nullable<T> overrides the equality operator to … Read more
You can use the qualities of the abstract equality operator to do this: Because null == undefined is true, the above code will catch both null and undefined.
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