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Core Java - Interview Questions and Answers for 'Runtime polymorphism' - 10 question(s) found - Order By Newest

 Q1. What are points to consider in terms of access modifier when we are overriding any method?Core Java
Ans. 1. Overriding method can not be more restrictive than the overridden method.

reason : in case of polymorphism , at object creation jvm look for actual runtime object. jvm does not look for reference type and while calling methods it look for overridden method.

If by means subclass were allowed to change the access modifier on the overriding method, then suddenly at runtime when the JVM invokes the true objects version of the method rather than the reference types version then it will be problematic

2. In case of subclass and superclass define in different package, we can override only those method which have public or protected access.

3. We can not override any private method because private methods can not be inherited and if method can not be inherited then method can not be overridden.

  Sample Code for Overriding

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   Like         Discuss         Correct / Improve     java   overriding   access specifier   inheritence   oops   polymorphism  object oriented programming (oops)  oops concepts   runtime polymorphism  object oriented programming (oops)  oops concepts     Asked in 4 Companies

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 Q2. If everything is an object , Cant we declare every object as

Object obj = new String();
Core Java
Ans. Yes, we can do that. Compiler wont complain. But using object reference we can only access methods which have been defined for object class i.e clone(), equals(), hashCode(), toString() etc.

We cannot access methods defined in String class or in any class in hierarchy between String and Object.

For example - we cannot do obj.append("abc") as it will now give compile time error.

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   Like         Discuss         Correct / Improve     object initialization  object declaration   runtime polymorphism  object oriented programming (oops)  oops concepts


 Q3. When are static and instance methods resolved ? During compile time or Runtime ?
Ans. Static methods are resolved during compile time and hence they cannot participate in runtime polymorphism. Instance methods are resolved during runtime.

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   Like         Discuss         Correct / Improve     java   static methods   methods   runtime polymorphism      intermediate


 Q4. Which of the following do you think is the primary reason you would never use a static class even the application doesn't need multiple requests or threads ?

a. Serialization
b. Runtime Polymorphism
c. Lazy Loading
d. Memory
Ans. Runtime Polymorphism

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   Like         Discuss         Correct / Improve     static class   static vs singleton   java   oops   objects  Runtime Polymorphism


 Q5. What is "dynamic method dispatch" in java ?Core Java
Ans. dynamic method dispatch is a process in which a call to an
overridden method is resolved at runtime rather than at compile-time. This is used to achieve runtime polymorphism in java.

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   Like         Discuss         Correct / Improve     overriding  runtime polymorphism  object oriented programming (oops)  oops concepts


 Q6. What is dynamic dispatch in Java ?Core Java
Ans. Dynamic dispatch in java is also known as runtime polymorphism.It is a process in which a call to an overriden method is resolved at runtime.

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   Like         Discuss         Correct / Improve     dynamic dispatch  runtime polymorphism  object oriented programming (oops)  oops concepts


 Q7. Is Runtime Polymorphism possible without Inheritance ?Core Java
Ans. Yes, Runtime Polymprohism requires either Class inheritance or Interface implementation.

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   Like         Discuss         Correct / Improve     runtime polymorphism  object oriented programming (oops)  oops concepts  method overriding  inheritance  object oriented programming (oops)  oops concepts


 Q8. What is virtual table with respect to method overriding in Java ?Core Java
 This question is still unanswered. Can you please provide an answer.


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   Like         Discuss         Correct / Improve     vtable  virtual method table   method overriding  runtime polymorphism  object oriented programming (oops)  oops concepts


 Q9. How is the virtual method table implemented in Java?Core Java
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   Like         Discuss         Correct / Improve     virtual method table   method overriding  runtime polymorphism  object oriented programming (oops)  oops concepts      expert        rare


 Q10. How many VTables are there for each class ? Core Java
Ans. There is one VTable for each class.

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   Like         Discuss         Correct / Improve     virtual table method  vtable  runtime polymorphism  object oriented programming (oops)  oops concepts   method overriding      intermediate        rare


 Q11. Runtime Polymorphism in Java is achieved through ..Core Java
a. Method Overloading
b. Method Overriding
c. Variable Overloading
d. Variable Overriding

Ans.b. Method Overriding


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