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Interface

 
Greenhorn
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What are all the similarities of interfaces and abstract class?
What are all the differences between interfaces and abstract class?
 
Greenhorn
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Dear Kesavan,
Similartities are :
1. Both are the means of declaring abstract methods.
2.Both forces its subclasses to implement the methods declared abstract in Interface/Abstract class.
3. In case the implementing/extending class doesn't provide implementation of abstract methods defined in Interface/Abstract class, the implementing class must be declared abstract.

Differences are :
1. A class can implement one or more interfaces at a time, on the other side, a class can extend only one class abstract or otherwise at a time.
2. Interfaces can't have concrete methods, while abstract classes may have concrete methods.
3. Variables defined in a Interface are final and static, while in an abstract class variables may be of any type.
4. In case of interface,methods implemented in the implementing class must declared as public. While in case of abstract classes, methods implemented in the extending class must be of the same signature as in the abstract class.
Hope, now get cleared !
Regards,
 
Ranch Hand
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hi,
some more differences are
1)abstract classes may have a constructor while a interface cannot have a constructor
2)methods in an abstract class may be private. while in interfaces they are public by default
abstract class y
{
y(){// constructor
System.out.println("in y");
}
}
class demo extends y
{
public static void main(String[] args)
{
demo xxx =new demo();
System.out.println("Hello World!");
}
}

prints out "in y"
"hello world"
Regds
Rahul.

[This message has been edited by rahul_mkar (edited June 27, 2000).]
 
KESAVAN RAMANUJAM
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hi raghul
thanks a lot
regards
kesavan
 
KESAVAN RAMANUJAM
Greenhorn
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hi sam
thanks a lot
regards
kesavan
 
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