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should abstart have returntrype compulsoryly

 
Ranch Hand
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What is the correct declaration of an abstract method that is intended to be public:

a)public abstract void add();
b)public abstract void add() {}
c)public abstract add();
d)public virtual add();
Select the most appropriate answer.

in this question the answeris given as a. why c also cannot be the answer.
 
Greenhorn
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The problem with answer c is it hasn't got a return type.
 
Greenhorn
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Because the method in c) doesn't have a return type.
 
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Every method must have a return type, even if it doesn't return anything (in which case its return type is void).

Notice that constructors seem to break that rule, but constructors are not really methods.
 
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