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Core Java - Interview Questions and Answers for 'Inheritence' - 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. Why every object constructor automatically call super() in Object before its own constructors?Core Java
Ans. Derived object carries the body of its class as well as the body of the parent class. Its body ( member elements ) is initialized using its own class constructor whereas the body ( member elements ) carried from the parent class are initialized using super class constructor. So In order to initialize the elements of the parent class before its own elements are even initialized, super is called.

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   Like         Discuss         Correct / Improve     java   oops   constructor   super   inheritance  object oriented programming (oops)  oops concepts   inheritence     Asked in 1 Companies      intermediate

 Q3. How compiler handles the exceptions in overriding ?Core Java
Ans. 1)The overriding methods can throw any runtime Exception , here in the case of runtime exception overriding method (subclass method) should not worry about exception being thrown by superclass method.

2)If superclass method does not throw any exception then while overriding, the subclass method can not throw any new checked exception but it can throw any runtime exception

3) Different exceptions in java follow some hierarchy tree(inheritance). In this case , if superclass method throws any checked exception , then while overriding the method in subclass we can not throw any new checked exception or any checked exception which are higher in hierarchy than the exception thrown in superclass method

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   Like         Discuss         Correct / Improve     java   overriding   exceptions   inheritence   inheritance  object oriented programming (oops)  oops concepts   oops

 Q4. what is covariant return type? Core Java
Ans. co-variant return type states that return type of overriding method can be subtype of the return type declared in method of superclass. it has been introduced since jdk 1.5

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   Like         Discuss         Correct / Improve     java   oops   inheritence   overriding   covariant return type   jdk5   advanced     Asked in 3 Companies      expert

  Q5. Does Java support Multiple Inheritance ?Core Java
Ans. Java doesn't support multiple inheritance. Interfaces does't facilitate inheritance and hence implementation of multiple interfaces doesn't make multiple inheritance.

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 Q6. Are constructors inherited? Can a subclass call the parent's class constructor? When?Core Java
Ans. You cannot inherit a constructor. That is, you cannot create a instance of a subclass using a constructor of one of it's superclasses. One of the main reasons is because you probably don't want to override the superclasses constructor, which would be possible if they were inherited. By giving the developer the ability to override a superclasses constructor you would erode the encapsulation abilities of the language.

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 Q7. Difference Between this() and super() ?Core Java
Ans. 1.this is a reference to the current object in which this keyword is used whereas super is a reference used to access members specific to the parent Class.

2.this is primarily used for accessing member variables if local variables have same name, for constructor chaining and for passing itself to some method whereas super is primarily used to initialize base class members within derived class constructor.

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 Q8. Can we reduce the visibility of the inherited or overridden method ?Core Java
Ans. No.

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   Like         Discuss         Correct / Improve     java   oops   access specifier   overriding   overridding   inheritence   yes-no

 Q9. Does a class inherit the constructor of its super class?
Ans. No.

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   Like         Discuss         Correct / Improve     java   oops   constructor   inheritence   constructor inheritance   yes no

 Q10. Why java doesn't support multiple Inheritence ?Core Java
Ans. class A {
void test() {
System.out.println("test() method");
}
}

class B {
void test() {
System.out.println("test() method");
}
}

Suppose if Java allows multiple inheritance like this,

class C extends A, B {
}

A and B test() methods are inheriting to C class.

So which test() method C class will take? As A & B class test() methods are different , So here we would Facing Ambiguity.

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