Take a look at below code: As you see while trying to access static field x via an uninitialized local variable Foo foo; code foo.x generates compilation error: Variable ‘foo’ might not have been initialized. It could seem like this error makes sense, but only until we realize that to access a sta…
Tag: initialization
Variable might be assigned in loop?
I don’t know why the code is not compiling when final variable is initialized in loop and loop iterate only one time? Is Loop is somehow running more than one time and multiple assignments is done to variable x? Answer The compiler does not care how many times the code in the loop will be executed at ru…
Is there a Lombok way to initialise a final field that is calculated from other fields?
I’m using Lombok to minimize code. Here’s my (contrived) situation in vanilla Java: I want to use lombok to generate the constructor and getters: To get the computation into the class, you might consider an instance block: but instance blocks are executed before code in the constructor executes, s…
How to autowire properties bean from Condition
Does have anyone way to autowire bean in Condition? There is an next example. We have 2 implementation of FileManager. One of implementation should be initialize in depends on property ‘platform’. Properties handles via Archaius. . . . This code doesn’t work. Main reason is because ArchaiusP…
Why do static and instance init blocks in Enums behave differently from those in Classes
In studying for the Java certification test I learned that static initialization blocks run once when the class is loaded, in order of appearance within the source code, that instance initialization blocks run each time an instance is created, and that code in constructors runs each time an instance is create…
How to use DispatcherListener in Struts 2
There is a interface DispatcherListener in Struts2. The docs says “A interface to tag those that want to execute code on the init and destroy of a Dispatcher.” But how to use this interface. If I create a class that implements this interface, how should I configure it to Struts2? Answer When a Dis…
Initialize field before super constructor runs?
In Java, is there any way to initialize a field before the super constructor runs? Even the ugliest hacks I can come up with are rejected by the compiler: Note: The issue disappeared when I switched from inheritance to delegation, but I would still like to know. Answer No, there is no way to do this. Accordin…
Necessity of static block in Java
I found that in Java, there is a feature called static block, which includes code that is executed when a class is first loaded (I don’t understand what ‘loaded’ means, does it mean initialized?). Is …
Java: “Local variable may not have been initialized” not intelligent enough?
Consider the following method: On x++ I get the “Local variable may not have been initialized” error. Clearly x will never be used uninitialized. Is there any way to suppress the warning except by initializing x? Thanks. Answer No, there is no way Java can examine all possible code paths for a pro…
How is a constructor executed?
I am making some revisions from the lecture slides and it says a constructor is executed in the following way: If the constructor starts with this, recursively execute the indicated constructor, then go to step 4. Invoke the explicitly or implicitly indicated superclass constructor (unless this class is java.…