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why do we need abstract classes when we have interfaces

 
Greenhorn
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why do we need abstract classes when we have interfaces ?
 
Marshal
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Because abstract classes can have implementations of methods.
Because abstract classes can have fields representing variables.
Because abstract classes can have constructors.
You sometimes need an intermediate form between an interface and a concrete (mutable) class; that is what abstract classes provide.
 
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Because you can implement more than one interface, whereas you can't extend more than one abstract class.
 
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