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What is the difference between interface and abstract class?

 
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as titled
 
Greenhorn
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the abstract class has one or more abstact method while in interface we have all the methods public and abstract by default. the data members in a class can be or can not be final but in interface they are final by default. one thing more u can implement more then one interface in a class but cant exteng more then one abstract class.
this was all wht i know abt that
may this helps u
 
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I found that a bit of a mouthful so I'll paraphrase:
An interface provides the default behaviour for a class without defining how any of that behaviour is implemented. (any class that implements java.lang.Comparable is guaranteed to have certain methods, but there is no specification on how those methods work)
An abstract class can also define the default methods for a class but can also implement some default behaviour for some of those methods. (java.io.InputStream defines the minimum methods an InputStream should have, as well as providing some default code for some of them)
Hope this helps. Interfaces and Abstract classes are important but a bit difficult to get your head around.
Dave
 
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The data members are also implicitly static, along with final, in an interface.
Along with everything Samer said, interfaces may also extend multiple superinterfaces, where as an abstract class is restricted to extending only one superclass. This allows for "multiple interface inheritance", so any class that implements an interface also implements all of the superinterfaces.
Basic thing to remember is abstract classes can have implementation, interfaces cannot.
Jason
 
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Abstract classes can generally provide what you would consider 'logical' inheritance.
e.g. vehicle > car or mammal > dog
Interfaces can provide links between hugely dissimilar classes.
e.g. in a drawing application an interface Drawable might be implemented by classes such as Triangle, EarthMover and Fish.
 
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thank you Colin. i need that visual cue in order to grasp these kinds of things. then, it's off to the races i go.
if i understand correctly, is an abstract class like a template of a class, only that the actions that objects of the class perform are not defined?
 
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