The field annotated @Autowired is null because Spring doesn’t know about the copy of MileageFeeCalculator that you created with new and didn’t know to autowire it. The Spring Inversion of Control (IoC) container has three main logical components: a registry (called the ApplicationContext) of components (beans) that are available to be used by the application, … Read more
JavaScript is very flexible with regards to checking for “null” values. I’m guessing you’re actually looking for empty strings, in which case this simpler code will work: if(!pass || !cpass || !email || !cemail || !user){ Which will check for empty strings (“”), null, undefined, false and the numbers 0 and NaN. Please note that … Read more
(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
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
First, make all current NULL values disappear: UPDATE [Table] SET [Column]=0 WHERE [Column] IS NULL Then, update the table definition to disallow “NULLs”: ALTER TABLE [Table] ALTER COLUMN [Column] INTEGER NOT NULL
In Python, the ‘null’ object is the singleton None. To check if something is None, use the is identity operator: if foo is None: …
undefined means a variable has been declared but has not yet been assigned a value: var testVar; alert(testVar); //shows undefined alert(typeof testVar); //shows undefined null is an assignment value. It can be assigned to a variable as a representation of no value: var testVar = null; alert(testVar); //shows null alert(typeof testVar); //shows object From the … Read more
No, a null check is not needed before using instanceof. The expression x instanceof SomeClass is false if x is null. The Java 11 Language Specification expresses this concisely in section 15.20.2, “Type comparison operator instanceof”. (Java 17 expresses this less concisely, after the introduction of instanceof patternmatching.) “At run time, the result of the … Read more
What is the cause? Bottom Line You are trying to use something that is null (or Nothing in VB.NET). This means you either set it to null, or you never set it to anything at all. Like anything else, null gets passed around. If it is null in method “A”, it could be that method … Read more
You can use the qualities of the abstract equality operator to do this: if (variable == null){ // your code here. } Because null == undefined is true, the above code will catch both null and undefined.