OOPs Concept ! - Why Static Methods can't be redefined in its subclass ?

Dear Experts ,
I had searched the SDN , but unable to find out the satisfactorily answers ..
Can anybody let me know the reason for the following Confusion in Oops Concept
Question 1: As we know , We can Inherit the Static Methods in the Sub Class , But we can't redefine it in the base class or Sub Class ?
Question 2 : Why can't Static Method be Abstract ?
Question 3 : Can a Class be Abstract or Final Both, If yes, then why ?
Thanks in Advance
Saurabh Goel

As per the above discussion two of your doubts have already been clarified so I am taking only third one.
A class cannot never be Abstract and final both coz Abstract signifies that the implementation of the class has not been defined completelyi.e. may be some methods have been defined but few methods are still missing implementation. 'Final' is used for those classes/methods which cannot be redefined means the complete implementation of the method has been defined no one can implement further logic under the same method.
If you are saying your method is Final then it cannot be overridden and Abstract implies that method implementation is yet to be defined which can only be implemented if that class/method is not 'Final'. So both the terms are contradictory.
Hope it clarifies!!!
Thanks,
Vishesh

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Can static methods overridden

help me to know that static methods can be overridden with example

No u can not override static,private or final methodsIt would be interesting for the OP to know why (the reason is very different in each of the three cases).
@OP: the same question was posted a fey days ago and I posted there a reply, if you do a search in the forum you'll find it.

Question about static method hiding

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I don't understand your point. In either case, static
or non-static, ExceptionB must be the same or a
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If you're unfamiliar with the concept of binary compatibility, read the chapter in the Java Language Specification. It's a critical but often overlooked aspect of the Java language.

What's wrong with static methods?

Answers on an postcard please.

I think the point here is that sometimes people come from a procedural background (or maybe no background) and they start with main, and one static method leads to another. They reach a tipping point where they are reluctant to define non-static methods to a class because it's all static elsewhere. And static method can't access instance data, so their data becomes largely static as well. When the dust settles, they are programming procedually in Java. So too many static methods is a sign that you may be programming procedurally instead of doing OOP, but using static appropriately is still cool.
And let's not get pedantic. What goes wrong if I make my String class's getLength method static?
public final class MyString {
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}It's a misuse of static, but it doesn't break my design.

Non-static method/object cannot be referenced from a static context...?????

What does this mean. I know about static, but I don't understand why I get this so many times.
I try to do something pretty normal and this is what I get a lot of times. I mean: the main() method should be static right? Then what good is the main() method if you cannot let it do stuff for you like this:
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}Why is this, what is the reason for Java to forbid this and what can I do about it?

Your draw() method, since it isn't defined as static is considered by Java to be part of your Test object; hence, it can only be invoked in the context of an existing instance of your object. In other words, any Java program that wanted to use your draw() method would have to create an instance of your Test class using something likemyTest = new Test()Your main method, however, is something different. Since you want to execute your class as a program, the Java run-time environment needs to have standard starting point. This starting point is the main method. The problem is that the main method must be static, because the run-time environment cannot be expected to know beforehand the correct way to create an instance of your class so that non-static methods can be invoked. The drawback is that your main method can only directly access methods that are defined as static.
There are two possible solutions to this problem, and which of the two you want to use depends on the object-oriented nature of your program.
On the one hand, if your draw() method is closely tied to the object itself, if the draw() method is actually drawing your object or a part of it, it should be left as an instance method, and you should simpy use the instance of the object you created in your main method:public static main( String args[] )
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Static methods in interfaces

Java cognoscenti,
Anyone know why I can't declare a method as static in an interface, but I can in an abstract class. Surely, semantically it's the same - defering the implementation of a static method, not an abstract class and an interface. By the way, I'm using JDK 1.2.2 if that makes a difference

No, it's not the same. You are not "defering the
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only abstract methods are allowed in interfaces.I didnt't know that. I thought that - because you can override static methods and you can call them onto an actual instance the method binding would be done at run-time, not at compile-time. So I was trying to prove you wrong, but you are correct !
A short summary of what I've learnt so far:
- interfaces cannot contain static methods
- abstract classes cannot contain abstract static methods
- static methods can be overriden, but they are not polymorphic; this means that the compiler decides which method to call at compile-time.
/* output
SuperClass.someMethod()
SubClass.someMethod()
SuperClass.someMethod()
SuperClass.someMethod()
SubClass.someMethod()
SubClass.someMethod()
SuperClass.someMethod()
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Static methods in interface (Yes, once again!)

I know there has been many questions about why static methods in interfaces are not allowed. I know it is forbidden by the JLS. But does anyone know the exact reason for this? Is it just a design issue or are there technical difficulties with allowing it?
I can't think of any reason that it should be impossible to allow static methods in interfaces. I don't even think it would be very difficult to do. More importantly, it could probably be done without breaking existing code and existing JVMs (not too sure about the last one).
So once again: Was the choice of not allowing static methods in interfaces a design choice or a technical choice?

A better example of what you are suggesting is surely ...
interface i {
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class a implements i {
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You cant call i.one() as the method doesn't exist without an instance of an implementing class.
To actually ever be able to use that method you would effectively be casting an INSTANCE of a or b -> i. If you have an instance of an a or b then there is absolutely no reason for that method to be static.
If you wanted to implement some sort of class (ie static) behaviour then class a could call its own internal static method from within the 'one' method.
To get right to the point ... there isn't one. If it gets added to the language (and I can't see it in my wildest dreams) then Sun have lost their marbles, surely?
Unless someone can give a good example of when it might be correct and useful to do so? I can't even see how it would be a convenience as it is completely unusable, no?

No static methods for Interfaces ?

Hi,
I was going though some documentation about the interfaces and it says that, an interface methods must not be static.
Can someone please explain or direct me in the direction which tell me why the internet methods cannot be static.
Thanx.
Mel

Defining a static method in a interface would be useless, since static methods can't be executed with dynamic binding. You'd have to know the name of the implementing class of the interface at compile time to call it, which would negate the need for an interface.
For more details google it, that question has been asked thousands of times.

Class constructor is actually "static" method, as Bruce Eckel says?

<Thinking in java> chapter 7 :
Even though constructors are not polymorphic (they?re actually static methods, but the static declaration is implicit), it?s important ...
Are constructors actually static methods? I do not think so. static method can only manipulate static members, but constructor can also deal with non-static members. In other words, constructor always associate with a object, while static method always associate with a class.
Why Mr. Eckel says that constructors are static?

From the JLS ?8.8.3
A constructor is always invoked with respect to an object, so it makes no sense for a constructor to be static, so no they are not.
Are constructors actually static methods?Constructor declarations are not members. Members are defined as the set fields, methods, nested classes and interfaces(JLS ?8). So they are not methods.

Advantages and disadvanteges with static methods

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A static method can't be overridden, and static methods are usually only used for some utility methods and other things which don't belong to the class. I would probably not make the methods static.
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JUnit : How to Mock Static Method

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The Limitation of this library is that only Interfaces can be mocked without any much effort and behavior can be set according to our needs.
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Since you would like to mock the static method, it is not part of the class you'd like to test, I assume. The class you do want to test is supposedly under your control and contains the static invocation. I'd suggest to refactor the use of the static invocation in the class being tested.
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OOPs Concept ! - Why Static Methods can't be redefined in its subclass ?

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