Defining an abstract class without any abstract methods

Question

Can I define an abstract class without adding an abstract method

User · Answer

Actually there is no mean if an abstract class doesnt have any abstract method   An abstract class is like a father  This father have some properties and behaviors when you as a child want to be a child of the father  father says the child you that must be this way  its our MOTO  and if you don t want to do  you are not my child

User · Answer

yes  we can declare an abstract class without any abstract method  the purpose of declaring a class as abstract is not to instantiate the class   so two cases   1  abstract class with abstract methods   these type of classes  we must inherit a class from this abstract class and must override the abstract methods in our class  ex  GenricServlet class  2  abstract class without abstract methods   these type of classes  we must inherit a class from this abstract class   ex  HttpServlet class purpose of doing is although you if you don t implement your logic in child class you can get the parent logic   please check the HttpServlet source code

User · Answer

Of course   Declaring a class abstract only means that you don t allow it to be instantiated on its own   Declaring a method abstract means that subclasses have to provide an implementation for that method   The two are separate concepts  though obviously you can t have an abstract method in a non-abstract class  You can even have abstract classes with final methods but never the other way around

User · Answer

You can  the question in my mind is more should you  Right from the beginning  I ll say that there is no hard and fast answer  Do the right thing for your current situation   To me inheritance implies an  is-a  relationship  Imagine a dog class  which can be extended by more specialized sub types  Alsatian  Poodle  etc   In this case making the dog class abstract may be the right thing to do since sub-types are dogs  Now let s imagine that dogs need a collar  In this case inheritance doesn t make sense  it s nonsense to have a  is-a  relationship between dogs and collars  This is definitely a  has-a  relationship  collar is a collaborating object  Making collar abstract just so that dogs can have one doesn t make sense   I often find that abstract classes with no abstract methods are really expressing a  has-a  relationship  In these cases I usually find that the code can be better factored without using inheritance  I also find that abstract classes with no abstract method are often a code smell and at the very least should lead to questions being raised in a code review   Again  this is entirely subjective  There may well be situations when an abstract class with no abstract methods makes sense  it s entirely up to interpretation and justification  Make the best decision for whatever you re working on

User · Answer

Yes  you can define an abstract class without an abstract method  However  if there is no method inside you might better go with an interface

User · Answer

Yes you can  The abstract class used in java signifies that you can t create an object of the class  And an abstract method the subclasses have to provide an implementation for that method   So you can easily define an abstract class without any abstract method   As for Example    public abstract class AbstractClass       public String nonAbstractMethodOne String param1 String param2           String param   param1   param2          return param             public static void nonAbstractMethodTwo String param           System out println  Value of param is   param             This is fine

User · Answer

Yes you can  Sometimes you may get asked this question that what is the purpose doing this  The answer is  sometimes we have to restrict the class from instantiating by its own  In that case  we want user to extend our Abstract class and instantiate child class

User · Answer

Yes we can have an abstract class without Abstract Methods as both are independent concepts  Declaring a class abstract means that it can not be instantiated on its own and can only be sub classed  Declaring a method abstract means that Method will be defined in the subclass

User · Answer

YES You can create abstract class with out any abstract method the best example of abstract class without abstract method is HttpServlet Abstract Method is a method which have no body  If you declared at least one method into the class  the class must be declared as an abstract its mandatory BUT if you declared the abstract class its not mandatory to declared the abstract method inside the class   You cannot create objects of abstract class  which means that it cannot be instantiated

User · Answer

Yes you can do it  Why don t you just try doing that

User · Answer

yes you can do that   declaring class abstract means that class will not be instantiated by any other class   and there should be at least one abstract method inside that and meaning of that you can declare abstract method in that class if you are not declaring method than its ok   example   public abstract class abs        protected int cx   0  cy   0       public void p             System out print  hello              this will work for sure

User · Answer

Yes  you can declare a class you cannot instantiate by itself with only methods that already have implementations  This would be useful if you wanted to add abstract methods in the future  or if you did not want the class to be directly instantiated even though it has no abstract properties

[java] Defining an abstract class without any abstract methods

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