Method overloading as well as overriding is 1 of the tricky concept to master copy as well as that's why its 1 of the most pop theme inwards Java Interviews. You volition often run across questions similar what is deviation betwixt overloading as well as overriding? or can y'all overload method inwards same class? during kickoff few rounds of interview, mostly at telephonic round. Since its business office of object oriented fundamentals its also skillful to know every bit much near these concepts every bit possible. In this article, I am sharing unopen to of the basic but oftentimes asked questions which are exclusively based upon overloading as well as overriding concept as well as their implementation inwards Java programming language. By going through these questions, You volition non only create good on interviews but also it volition improve your agreement of Java as well as OOP fundamentals. BTW, if y'all are seriously preparing for Java interviews, only preparing this theme volition non live plenty as well as y'all demand to gear upward other of import topics every bit good e.g. Java Collection framework, multi-threading, JVM internals as well as garbage collections etc. If y'all are inwards hurry, I would propose y'all to bring a hold off at Java Programming Interview Exposed past times Wrox publication, 1 of the amend majority on Java interviews.
1) What is method overloading inwards Java?
If y'all receive got 2 method which does same affair its amend they receive got same name, but 2 method cannot receive got same cite until y'all overload them. So overloading is a procedure of declaring 2 methods alongside same cite but dissimilar method signature e.g. System.out which is object of PrintStream flat has several println() method to impress dissimilar information types e.g. byte, short, int, char, float as well as double. All of them are called overloaded method. Overloaded method calls are resolved during compile fourth dimension inwards Java as well as they must receive got dissimilar method signatures. See here to acquire to a greater extent than near method overloading inwards Java.
2) What is method overriding inwards Java?
Method overriding is unopen to other way to define method alongside same cite but dissimilar code but it must live inwards sub class. Overriding is based upon run-time Polymorphism every bit method calls are resolved at run-time depending upon actual object. For representative if a variable of type Parent holds an object of Child flat as well as so method invoked volition live from fry flat as well as non raise class, provides its overridden. In social club to override a method, y'all must follow rules of method overriding which way declaring method alongside same signature inwards sub class. See here to acquire to a greater extent than near method overriding inwards Java.
3) What is method hiding inwards Java?
static method cannot live overriding inwards Java because their method calls are resolved at compile fourth dimension but it didn't forestall y'all from declaring method alongside same cite inwards sub class. In this representative nosotros say that method inwards sub flat has hided static method from raise class. If y'all receive got a representative where variable of Parent flat is pointing to object of Child flat as well as so also static method from Parent flat is called because overloading is resolved at compile time. See here to acquire to a greater extent than near method hiding inwards Java.
4) What are rules of overloading a method inwards Java?
One as well as only dominion of method overloading inwards Java is that method signature of all overloaded method must live different. Method signature is changed past times changing either publish of method arguments, or type of method arguments e.g. System.out.println() method is overloaded to bring dissimilar primitive types similar int, short, byte, float etc. They all bring only 1 declaration but their type is different. You tin post away also alter method signature past times changing social club of method declaration but that often leads to ambiguous code so amend to live avoided. See here for sum listing of rules.
5) Difference betwixt method overloading as well as overriding?
Fundamental deviation betwixt overloading as well as overriding is that quondam took house during compile fourth dimension land later on took house during run-time. Due to this reason, its only possible to overload virtual methods inwards Java. You cannot overload methods which are resolved during compile fourth dimension e.g. private, static as well as lastly method cannot live overridden inwards Java. Also, rules of method overloading as well as overriding are different, for representative inwards social club to overload a method its method signature must live dissimilar but for overriding method it must live same. See this image to acquire to a greater extent than deviation betwixt overriding as well as overloading inwards Java.
6) Can nosotros overload static method inwards Java?
Yes, its possible to overload static method inwards Java. You tin post away declare every bit many static method alongside same cite every bit y'all desire until all of them receive got dissimilar method signature. Remember, render type is non business office of method signature, so they must receive got either dissimilar publish of arguments, or dissimilar type of argument. There is a tertiary choice also which changes social club of declaration but I propose non to create that because it often lawsuit inwards ambiguous method call. It's really of import to follow these best practices land overloading a static method inwards Java.
7) Can nosotros override static method inwards Java?
No, y'all cannot override static method inwards Java because they are resolved as well as bonded during compile time. Since overriding is a run-time action as well as if a method telephone weep upward is already resolved at compile fourth dimension as well as so it volition non bring house as well as that's why its non possible to override static method inwards Java. But, y'all tin post away define unopen to other static method of same signature inwards sub class, this is known every bit method hiding. Actual method called volition depends upon the type of flat as well as non on type of object every bit its the representative alongside overriding. See here to acquire to a greater extent than near why y'all cannot override static method inwards Java.
8) Can y'all forestall overriding a method without using lastly modifier?
Yes, at that topographic point are unopen to funky ways to forestall method overriding inwards Java. Though lastly modifier is only for that role y'all tin post away utilization someone keyword to forestall method overriding. How? If y'all holler back correctly, inwards social club to override a method, the flat must live extensible. If y'all brand the constructor of raise flat someone as well as so its non possible to extend that flat because its constructor volition non live accessible inwards sub class, which is automatically invoked past times sub flat constructor, therefore its non possible to override whatever method from that class. This technique is used inwards Singleton blueprint pattern, where constructor is purposefully made someone as well as a static getInstance() method is provided to access singleton instance. See here to acquire to a greater extent than techniques to forestall method overriding inwards Java.
9) Can nosotros override a someone method inwards Java?
No, y'all cannot override someone method inwards Java. Since someone methods are non visible exterior the class, they are non available inwards sub-class therefore they cannot live overridden. By the way, how near overriding a someone method within an Inner class? Is it possible? See here to acquire to a greater extent than why y'all cannot override someone method inwards Java.
10) What is co-variant method overriding?
One of the dominion of method overriding is that render type of overriding method must live same every bit overridden method but this restriction is relaxed piffling chip from Java 1.5 as well as immediately overridden method tin post away render sub flat of render type of original method. This relaxation is known every bit co-variant method overriding as well as it allows y'all to withdraw casting at customer end. One of the best representative of this comes when y'all override clone() method. Original Object.clone() method returns Object which needs to cast, but alongside co-variant method overriding y'all tin post away straight render relevant type e.g. Date flat returns object of java.util.Date instead of java.lang.Object. See hither to acquire to a greater extent than near co-variant method overriding inwards Java.
11) Can nosotros alter declaration listing of overridden method?
No, y'all cannot alter the declaration listing of overridden method inwards Java. An overriding method must receive got same signature every bit original method. Only render type tin post away live changed that to only to sub type of render type of original method.
12) Can nosotros alter render type of method inwards subclass land overriding?
No, y'all cannot alter the render type of method during overriding. It would live violation of rules of overriding. Though from Java five onward y'all tin post away supplant the render type alongside sub type e.g. if original method has render type every bit java.lang.Object as well as so y'all tin post away alter render type of overridden method every bit whatever type e.g. clone() method. This is also known every bit co-variant method overriding inwards Java.
13) Can nosotros override a method which throws run-time exception without throws clause?
Yes, y'all can. There is no restriction on throwing RuntimeException from overriding method. So if your original method throws NullPointerException than its non necessary to throw NPE from overriding method every bit well.
14) How create y'all telephone weep upward super flat version of an overriding method inwards sub class?
You tin post away telephone weep upward it using super keyword. For representative if y'all receive got a method calculate() inwards both raise as well as fry flat as well as so from fry flat y'all tin post away invoke raise flat method calculate() every bit super.calculate(). It's really similar to calling super flat constructor from sub flat every bit shown here.
15) What are rules of method overriding inwards Java?
Some rules of method overriding are next :
16) Can nosotros override a non-static method every bit static inwards Java?
No, its non possible to define a non-static method of same cite every bit static method inwards raise class, its compile fourth dimension mistake inwards Java. See hither to acquire to a greater extent than near overriding static method inwards Java.
17) Can nosotros override constructor inwards Java?
No, y'all cannot override constructor inwards Java because they are non inherited. Remember, nosotros are talking near overriding hither non overloading, y'all tin post away overload build but y'all cannot override them. Overriding ever happens at fry flat as well as since constructor are non inherited as well as their cite is ever same every bit the flat cite its non possible to override them inwards Java, to acquire to a greater extent than near constructor run across here
18) Can nosotros override lastly method inwards Java?
No, y'all cannot override lastly method inwards Java. Trying to override lastly method inwards subclass volition lawsuit inwards compile fourth dimension error. Actually making a method lastly is signal to all developer that this method is non for inheritance as well as it should live utilization inwards its introduce form. You by as well as large brand a method lastly due to safety reasons, to acquire to a greater extent than run across here.
19) Can y'all overload or override master copy method inwards Java?
Since main() is a static method inwards Java, it follows rules associated alongside static method, which way y'all tin post away overload master copy method but y'all cannot override it. By the way, fifty-fifty if y'all overload a master copy method, JVM volition ever telephone weep upward the criterion public static void main(String args[]) method to start your program, if y'all desire to telephone weep upward your overloaded method y'all demand to create it explicitly inwards your code every bit shown here.
That's all near unopen to Java interview questions from method overloading as well as overriding concept. I must acknowledge its a tricky concept to master. I receive got seen fifty-fifty experienced developer struggling to solve quiz as well as multiple selection questions based upon overloading as well as overriding. So, if y'all desire to create good on Java Interviews every bit good every bit wants to write good, powerful as well as flexible code using object oriented programming technique, spare unopen to fourth dimension to sympathize overloading as well as overriding inwards Java. It volition assistance y'all to leverage Polymorphism better.
If y'all are interested on unopen to to a greater extent than Java interview questions based upon dissimilar topics as well as so y'all tin post away also run across next lists, which includes questions from multi-threading, collection framework, JDBC, frameworks, blueprint patterns, spider web services as well as several other topics :
Overloading as well as Overriding Interview Questions
Ok, let's start on questions. Here is my listing of 17 method overloading as well as overriding interview query which covers basics every bit good every bit unopen to tricky business office of overloading as well as overriding. You tin post away also write unopen to code to examine the concept as well as run across when compiler gives mistake as well as which method is acquire called at run-time.1) What is method overloading inwards Java?
If y'all receive got 2 method which does same affair its amend they receive got same name, but 2 method cannot receive got same cite until y'all overload them. So overloading is a procedure of declaring 2 methods alongside same cite but dissimilar method signature e.g. System.out which is object of PrintStream flat has several println() method to impress dissimilar information types e.g. byte, short, int, char, float as well as double. All of them are called overloaded method. Overloaded method calls are resolved during compile fourth dimension inwards Java as well as they must receive got dissimilar method signatures. See here to acquire to a greater extent than near method overloading inwards Java.
2) What is method overriding inwards Java?
Method overriding is unopen to other way to define method alongside same cite but dissimilar code but it must live inwards sub class. Overriding is based upon run-time Polymorphism every bit method calls are resolved at run-time depending upon actual object. For representative if a variable of type Parent holds an object of Child flat as well as so method invoked volition live from fry flat as well as non raise class, provides its overridden. In social club to override a method, y'all must follow rules of method overriding which way declaring method alongside same signature inwards sub class. See here to acquire to a greater extent than near method overriding inwards Java.
3) What is method hiding inwards Java?
static method cannot live overriding inwards Java because their method calls are resolved at compile fourth dimension but it didn't forestall y'all from declaring method alongside same cite inwards sub class. In this representative nosotros say that method inwards sub flat has hided static method from raise class. If y'all receive got a representative where variable of Parent flat is pointing to object of Child flat as well as so also static method from Parent flat is called because overloading is resolved at compile time. See here to acquire to a greater extent than near method hiding inwards Java.
4) What are rules of overloading a method inwards Java?
One as well as only dominion of method overloading inwards Java is that method signature of all overloaded method must live different. Method signature is changed past times changing either publish of method arguments, or type of method arguments e.g. System.out.println() method is overloaded to bring dissimilar primitive types similar int, short, byte, float etc. They all bring only 1 declaration but their type is different. You tin post away also alter method signature past times changing social club of method declaration but that often leads to ambiguous code so amend to live avoided. See here for sum listing of rules.
5) Difference betwixt method overloading as well as overriding?
Fundamental deviation betwixt overloading as well as overriding is that quondam took house during compile fourth dimension land later on took house during run-time. Due to this reason, its only possible to overload virtual methods inwards Java. You cannot overload methods which are resolved during compile fourth dimension e.g. private, static as well as lastly method cannot live overridden inwards Java. Also, rules of method overloading as well as overriding are different, for representative inwards social club to overload a method its method signature must live dissimilar but for overriding method it must live same. See this image to acquire to a greater extent than deviation betwixt overriding as well as overloading inwards Java.
6) Can nosotros overload static method inwards Java?
Yes, its possible to overload static method inwards Java. You tin post away declare every bit many static method alongside same cite every bit y'all desire until all of them receive got dissimilar method signature. Remember, render type is non business office of method signature, so they must receive got either dissimilar publish of arguments, or dissimilar type of argument. There is a tertiary choice also which changes social club of declaration but I propose non to create that because it often lawsuit inwards ambiguous method call. It's really of import to follow these best practices land overloading a static method inwards Java.
7) Can nosotros override static method inwards Java?
No, y'all cannot override static method inwards Java because they are resolved as well as bonded during compile time. Since overriding is a run-time action as well as if a method telephone weep upward is already resolved at compile fourth dimension as well as so it volition non bring house as well as that's why its non possible to override static method inwards Java. But, y'all tin post away define unopen to other static method of same signature inwards sub class, this is known every bit method hiding. Actual method called volition depends upon the type of flat as well as non on type of object every bit its the representative alongside overriding. See here to acquire to a greater extent than near why y'all cannot override static method inwards Java.
8) Can y'all forestall overriding a method without using lastly modifier?
Yes, at that topographic point are unopen to funky ways to forestall method overriding inwards Java. Though lastly modifier is only for that role y'all tin post away utilization someone keyword to forestall method overriding. How? If y'all holler back correctly, inwards social club to override a method, the flat must live extensible. If y'all brand the constructor of raise flat someone as well as so its non possible to extend that flat because its constructor volition non live accessible inwards sub class, which is automatically invoked past times sub flat constructor, therefore its non possible to override whatever method from that class. This technique is used inwards Singleton blueprint pattern, where constructor is purposefully made someone as well as a static getInstance() method is provided to access singleton instance. See here to acquire to a greater extent than techniques to forestall method overriding inwards Java.
9) Can nosotros override a someone method inwards Java?
No, y'all cannot override someone method inwards Java. Since someone methods are non visible exterior the class, they are non available inwards sub-class therefore they cannot live overridden. By the way, how near overriding a someone method within an Inner class? Is it possible? See here to acquire to a greater extent than why y'all cannot override someone method inwards Java.
10) What is co-variant method overriding?
One of the dominion of method overriding is that render type of overriding method must live same every bit overridden method but this restriction is relaxed piffling chip from Java 1.5 as well as immediately overridden method tin post away render sub flat of render type of original method. This relaxation is known every bit co-variant method overriding as well as it allows y'all to withdraw casting at customer end. One of the best representative of this comes when y'all override clone() method. Original Object.clone() method returns Object which needs to cast, but alongside co-variant method overriding y'all tin post away straight render relevant type e.g. Date flat returns object of java.util.Date instead of java.lang.Object. See hither to acquire to a greater extent than near co-variant method overriding inwards Java.
11) Can nosotros alter declaration listing of overridden method?
No, y'all cannot alter the declaration listing of overridden method inwards Java. An overriding method must receive got same signature every bit original method. Only render type tin post away live changed that to only to sub type of render type of original method.
12) Can nosotros alter render type of method inwards subclass land overriding?
No, y'all cannot alter the render type of method during overriding. It would live violation of rules of overriding. Though from Java five onward y'all tin post away supplant the render type alongside sub type e.g. if original method has render type every bit java.lang.Object as well as so y'all tin post away alter render type of overridden method every bit whatever type e.g. clone() method. This is also known every bit co-variant method overriding inwards Java.
13) Can nosotros override a method which throws run-time exception without throws clause?
Yes, y'all can. There is no restriction on throwing RuntimeException from overriding method. So if your original method throws NullPointerException than its non necessary to throw NPE from overriding method every bit well.
14) How create y'all telephone weep upward super flat version of an overriding method inwards sub class?
You tin post away telephone weep upward it using super keyword. For representative if y'all receive got a method calculate() inwards both raise as well as fry flat as well as so from fry flat y'all tin post away invoke raise flat method calculate() every bit super.calculate(). It's really similar to calling super flat constructor from sub flat every bit shown here.
15) What are rules of method overriding inwards Java?
Some rules of method overriding are next :
- Overriding method cannot throw higher exception than overridden one, but that's only truthful for checked exception.
- Overriding method cannot confine access of overridden method e.g. if original method is populace as well as so overriding method must live public, but it tin post away expand access e.g. if original method is protected than overriding method tin post away live protected or public.
16) Can nosotros override a non-static method every bit static inwards Java?
No, its non possible to define a non-static method of same cite every bit static method inwards raise class, its compile fourth dimension mistake inwards Java. See hither to acquire to a greater extent than near overriding static method inwards Java.
17) Can nosotros override constructor inwards Java?
No, y'all cannot override constructor inwards Java because they are non inherited. Remember, nosotros are talking near overriding hither non overloading, y'all tin post away overload build but y'all cannot override them. Overriding ever happens at fry flat as well as since constructor are non inherited as well as their cite is ever same every bit the flat cite its non possible to override them inwards Java, to acquire to a greater extent than near constructor run across here
18) Can nosotros override lastly method inwards Java?
No, y'all cannot override lastly method inwards Java. Trying to override lastly method inwards subclass volition lawsuit inwards compile fourth dimension error. Actually making a method lastly is signal to all developer that this method is non for inheritance as well as it should live utilization inwards its introduce form. You by as well as large brand a method lastly due to safety reasons, to acquire to a greater extent than run across here.
19) Can y'all overload or override master copy method inwards Java?
Since main() is a static method inwards Java, it follows rules associated alongside static method, which way y'all tin post away overload master copy method but y'all cannot override it. By the way, fifty-fifty if y'all overload a master copy method, JVM volition ever telephone weep upward the criterion public static void main(String args[]) method to start your program, if y'all desire to telephone weep upward your overloaded method y'all demand to create it explicitly inwards your code every bit shown here.
That's all near unopen to Java interview questions from method overloading as well as overriding concept. I must acknowledge its a tricky concept to master. I receive got seen fifty-fifty experienced developer struggling to solve quiz as well as multiple selection questions based upon overloading as well as overriding. So, if y'all desire to create good on Java Interviews every bit good every bit wants to write good, powerful as well as flexible code using object oriented programming technique, spare unopen to fourth dimension to sympathize overloading as well as overriding inwards Java. It volition assistance y'all to leverage Polymorphism better.
If y'all are interested on unopen to to a greater extent than Java interview questions based upon dissimilar topics as well as so y'all tin post away also run across next lists, which includes questions from multi-threading, collection framework, JDBC, frameworks, blueprint patterns, spider web services as well as several other topics :
- Top xx ArrayList based Java Interview Questions as well as Answers [article]
- 40 Core Java Questions from Phone Interviews [list]
- 15 Java Enum Interview Questions alongside Answers as well as Explanations [questions]
- 18 Java Interview Questions based upon GOF Design Patterns as well as OOP [questions]
- Top 21 Frequently asked Java interview questions for freshers [article]
- 12 Java Multithreading as well as Concurrency based Interview Questions [see here]
- JDBC Interview Questions as well as Answers for 2 to four years experienced developers [see here]
- 10 Spring Framework based Interview Questions [article]
- 10 Must know Java Collection framework Interview Questions as well as Answers [read here]
- 10 Java Web Services based Questions [list]
- Top 10 Advanced Java Questions for Experienced as well as Senior Programmers [see here]
- 22 Array concepts based Interview Questions inwards Java? [answers]
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