This question already has answers here:
Closed 10 years ago.
Possible Duplicate:
What’s “#Override” there for in java?
Since Java 1.5 this annotation was incorporated to the language to be used on methods that overwrite a superclass methods.
Now, what changes in a method that uses this annotation to one that doesn't use it? Is this just convention?
Assuming, obviously, that both be methods that overwrite a method from its superclass...
#Override creates a compile-time check that a method is being overridden.
This is very useful to make sure you do not have a silly signature issue when trying to override
It not only makes the compiler check but also documents the
developer's intention.
if you override a method but don't use it anywhere from the type itself, someone coming to the code later may know the purpose. The annotation explains its purpose.
A good IDE will helpfully flag any method that overrides a method without #Override, so the combination of the two will help ensure that you're doing what you're trying to.
it also improves readability
Related
This question already has answers here:
Which types can be used for Java annotation members?
(4 answers)
Closed 4 years ago.
Can I able to call a method which returns string inside an annotation.
If so please guide me how to achieve this?
I tried like this but this doesn't work for me.
#Description(value = Resource.getWord("key"))
An annotation only takes compile time constants (as they might be used during compile time), therefore you cannot make any calculation within the definition, as they are unknown during the compile time.
Allowed constant types are (taken from java-annotation-members):
Primitive
String
Class
Enum
Another Annotation
An array of any of the above
Possible solution for your situation:
As I understand you would like to localize the #Description content.
As this is only meant to be exposed to other developers anyway, you are safe to simply use English, in my opinion. Localization is for the end user, not the developer.
I can imagine an aspect being wired up to process methods annotated like this, where the "key" is in the annotation, and the aspect processing then uses the key at run time... but I'm not sure this is what you're looking for.
This question already has answers here:
What is the "default" implementation of method defined in an Interface?
(3 answers)
Closed 6 years ago.
I was studying lambada and there was a point which states that in java 8 we can declare a method with definition in interfaces like
interface Test {
default String method(){
return "string";
}
}
and as per specification we can use two methods with same signature but depends on programmer how he wants to use it?
Now the question is same task can be if achieved by using definition not declaration then what's the point of using default method?
like they behave same as regular method definition and programmer need to declare body and rest part?
what is the actual point as it seems a bit hard to grasp
thanks #ElliottFrisch and #kagemusha for hint after searching i got the answer
Why default methods?
List<?> list = …
list.forEach(…); // lambda code goes here
The forEach isn’t declared by java.util.List nor the java.util.Collection interface yet. One obvious solution would be to just add the new method to the existing interface and provide the implementation where required in the JDK. However, once published, it is impossible to add methods to an interface without breaking the existing implementation.
So it’d be really frustrating if we have lambdas in Java 8 but couldn’t use those with the standard collections library since backwards compatibility can’t be sacrificed.
Due to the problem described above a new concept was introduced. Virtual extension methods, or, as they are often called, defender methods, can now be added to interfaces providing a default implementation of the declared behavior.
Simply speaking, interfaces in Java can now implement methods. The benefit that default methods bring is that now it’s possible to add a new default method to the interface and it doesn’t break the implementations.
It doesn’t seem to be the language feature that would be appropriate to use every day, but it seems to be essential for Java Collections API update to be able to use lambdas naturally.
This question already has answers here:
Closed 10 years ago.
Possible Duplicate:
The constructor Date(…) is deprecated. What does it mean? (Java)
When I use SMSManager object on Android, Eclipse notice that this class is deprecate and there is a crossline at SMSManager, but everything works normally.
Who can explain for me this, please.
thanks :)
#Deprecated
A program element annotated #Deprecated is one that programmers are discouraged from using, typically because it is dangerous, or because a better alternative exists. Compilers warn when a deprecated program element is used or overridden in non-deprecated code.
A deprecated class or method is one that programmers are discouraged from using, typically because it is dangerous, or because a better alternative exists. It is so potentially bad/out-dated, in fact, that you should no longer use it, since it has been superseded and may cease to exist in the future.
Deprecated means it will no longer be supported in the future. See the documentation http://developer.android.com/reference/android/telephony/gsm/SmsManager.html
This class is deprecated.
Replaced by android.telephony.SmsManager that supports both GSM and CDMA.
This class is deprecated.
Replaced by android.telephony.SmsManager that supports both GSM and CDMA.
See here
Deprecation doesn't mean that the Object isn't working anymore, it means that a new one exists now and that you should be using that new one. In your case, you should use android.telephony.SMSManager and not android.telephony.gsm.SMSManager.
This question already has answers here:
Closed 11 years ago.
Possible Duplicate:
How do you find all subclasses of a given class in Java?
I have a super class, MyClass, and it is abstract. Anyone can implement it.
At runtime, I need to determine which classes have inherited from this class, using java reflection. How can one do this?
You can use the Reflections library.
Using Reflections you can query your metadata such as:
get all subtypes of some type
get all types/methods/fields annotated with some annotation, w/o
annotation parameters matching
get all resources matching matching a regular expression
A tutorial about that is Java Tip 113: Identify subclasses at runtime.
The only way to do it (without resorting to external libraries) is to loop through all your classes and check them individually - there's no efficient method built in (nor can there really be, how else would you do it than scanning all the classes since they can be loaded dynamically?)
See Stack Overflow question How do you find all subclasses of a given class in Java? for much more detail.
This question already has answers here:
Closed 12 years ago.
I have a class which inherits from two different interfaces. Both interfaces declare a method with the same name. How can I provide a different implementation for each interface ?
In C#, the answer is there, but it does not work in java:
Inheritance from multiple interfaces with the same method name
I thought about providing a union implementation which uses type comparison but it's kind of ugly.
Thanks
EDIT : closed, my question was a duplicate of the following, thank you for the answers !
Java - Method name collision in interface implementation
You can't. Interfaces describe behavior, but they don't implement it. So if you implement a method, there's no way to tell which interface you are implementing it from.
No, there's no equivalent feature in Java.
And you can't do it yourself, because inside the method, you have no way of telling if the calling code is referencing the object as InterfaceA or InterfaceB. Even if you could, I think it would be a bad idea.