Difference Betwixt Method Overloading As Well As Overriding Inwards Java?

Method Overloading vs Method Overriding

Though the mention of the method remains same inward the instance of both method overloading in addition to overriding, original divergence comes from the fact that method overloading is resolved during compile time, piece method overriding is resolved at runtime. Also rules of overriding or overloading a method are dissimilar inward Java. For example, a private, static in addition to concluding method cannot hold upwardly overriding inward Java but you lot tin all the same overload them. For overriding both mention in addition to signature of the method must rest same, but inward for overloading method, the signature must hold upwardly different. Last but non the to the lowest degree divergence betwixt them is that telephone telephone to overloaded methods are resolved using static binding piece the telephone telephone to overridden method is resolved using dynamic binding inward Java.

By the way, Method overloading in addition to method overriding inward Java is 2 of import concept inward Java which allows Java programmer to declare method amongst same mention but dissimilar behavior. Method overloading in addition to method overriding is based on Polymorphism inward Java.

In instance of method overloading, method amongst same mention co-exists inward same shape but they must possess got dissimilar method signature, piece inward instance of method overriding, method amongst same mention is declared inward derived shape or sub class.Method overloading is resolved using static binding inward Java at compile fourth dimension piece method overriding is resolved using dynamic binding inward Java at runtime.

In short, when you lot overload a method inward Java its method signature got changed piece inward instance of overriding method signature remains same but a method tin alone hold upwardly overridden inward sub class. Since Java supports Polymorphism in addition to resolve object at run-time it is capable to telephone telephone overridden method inward Java.

By the way divergence betwixt method overloading in addition to overriding is too i of the pop Java pattern question in addition to appear inward almost all levels of Java interviews.

What is method overloading in addition to overriding inward Java?

In this Java tutorial nosotros volition meet how Java allows you lot to create 2 methods of same mention past times using method overloading in addition to method overriding. We volition too touching on base of operations on how methods are bonded or called past times Compiler in addition to Java Virtual Machine in addition to in conclusion nosotros volition response of pop interview questions divergence betwixt method overloading in addition to method overriding inward Java.

This article is inward my serial of Java article which discusses close Interview e.g. Difference betwixt Synchronized Collection in addition to Concurrent Collection or How to Stop Thread inward Java. Please allow me know if you lot possess got another interview questions in addition to you lot are looking response or argue for that in addition to hither inward nosotros volition effort to discovery in addition to hash out those interview questions.

How to Overload a Method inward Java

If you lot possess got 2 methods amongst same mention inward i Java shape amongst dissimilar method signature than its called overloaded method inward Java. Generally overloaded method inward Java has dissimilar develop of arguments to perform something based on dissimilar release of input.

You tin too overload constructor inward Java, which nosotros volition meet inward next illustration of method overloading inward Java. Binding of overloading method occurs during compile fourth dimension in addition to overloaded calls resolved using static binding. To overload a Java method just changes its signature.

Just retrieve inward fellowship to modify signature you lot either demand to modify release of argument, type of declaration or fellowship of declaration inward Java if they are of dissimilar types. Since provide type is non component of method signature just changing provide type volition lawsuit inward duplicate method in addition to you lot volition acquire compile fourth dimension mistake inward Java.

In our illustration of Loan in addition to PersonalLoan class, createLoan method is overloaded. Since you lot possess got 2 crateLoan() method amongst i takes i declaration lender piece other accept 2 declaration both lender in addition to interestRate. Remember you lot tin overload static method inward Java, you lot tin too overload individual in addition to final method inward Java but you lot tin non override them.

How to Override a Method inward Java

In fellowship to override a Java method, you lot demand to create a tike shape which extends parent. Overridden method inward Java too shares same mention equally original method inward Java but tin alone hold upwardly overridden inward sub class. Original method has to hold upwardly defined within interface or base of operations class, which tin hold upwardly abstract as well. When you lot override a method inward Java its signature remains precisely same including provide type. JVM resolves right overridden method based upon object at run-time past times using dynamic binding inward Java. For illustration inward our instance when nosotros telephone telephone personalLoan.toString() method fifty-fifty though personalLoan object is of type Loan actual method called would hold upwardly from PersonalLoan shape because object referenced past times personalLoan variable is of type PersonalLoan(). This is real useful technique to modify deportment of a component inward Java based on dissimilar implementation. equals(), hashcode() in addition to compareTo() methods are classic illustration of overridden methods inward Java.

Another of import signal is that you lot tin non override static method inward Java because they are associated amongst Class rather than object in addition to resolved in addition to bonded during compile fourth dimension in addition to that’s the argue you lot cannot override original method inward Java. Similar to static, individual in addition to concluding methods are too non overridden inward Java. By the way, equally component of overriding best practice, ever use @Override annotation, piece overriding method from an abstract shape or interface.

Rules of Method Overriding inward Java

Following are rules of method overriding inward coffee which must hold upwardly followed piece overriding whatever method. As stated before private, static in addition to final method tin non hold upwardly overridden inward Java. 

1. Method signature must hold upwardly same including provide type, release of method parameters, type of parameters in addition to fellowship of parameters 
2. Overriding method tin non throw higher Exception than original or overridden method. agency if original method throws IOException than overriding method tin non throw super shape of IOException e.g. Exception but it tin throw whatever sub shape of IOException or just does non throw whatever Exception. This dominion alone applies to checked Exception inward Java, overridden method is complimentary to throw whatever unchecked Exception. 
3. Overriding method tin non cut down accessibility of overridden method , agency if original or overridden method is populace than overriding method tin non arrive protected. 

Difference betwixt Method Overloading vs Overriding inward Java

Overloading vs Overriding inward Java is i of the popular coffee interview questions at many companies in addition to asked at dissimilar levels of programmers. Here are to a greater extent than or less of import divergence betwixt overloading in addition to overriding inward Java. Though It's to a greater extent than of import is to empathize how to role both overloading in addition to overriding, these divergence are skilful from interview perspective in addition to gives to a greater extent than or less basic thought equally well:

1) First in addition to most of import divergence betwixt method overloading in addition to overriding is that, In instance of method overloading inward Java, signature of method changes piece inward instance of method overriding it rest same.

2) Second major divergence betwixt method overloading vs overriding inward Java is that You tin overload method inward i shape but overriding tin alone hold upwardly done on subclass.

3) You tin non override static, final in addition to private method inward Java but you lot tin overload static, concluding or individual method inward Java.

4) Overloaded method inward Java is bonded past times static binding in addition to overridden methods are plain of report to dynamic binding.

5) Private in addition to concluding method tin too hold upwardly non overridden inward Java.

By the way, you lot mightiness possess got heard close "a painting present is worth to a greater extent than than one one thousand words" in addition to this is made truthful past times next image. By looking at the pic you lot tin clearly empathize divergence betwixt method overloading in addition to overriding inward Java. 

Handling Exception piece overloading in addition to overriding method inward Java

While overriding a method it tin alone throw checked exception declared past times by overridden method or whatever subclass of it, agency if overridden method throws IOExcpetion than overriding method tin throw sub classes of IOExcpetion e.g. FileNotFoundException but non wider exception e.g. Exception or Throwable. This restriction is alone for checked Exception for RuntimeException you lot tin throw whatever RuntimeException. Overloaded method inward Java doesn't possess got such restriction in addition to you lot are complimentary to modify throws clause equally per your need.

Method Overloading in addition to Overriding Example inward Java

Here is an illustration of both method overloading in addition to method overriding inward Java. In fellowship to explicate the concept nosotros possess got create 2 classes Loan and PersonalLoan. createLoan() method is overloaded equally it has dissimilar version amongst dissimilar signature, piece toString() method which is original declared inward Object shape is overridden inward both Loan in addition to PersonalLoan class.

public class OverloadingOverridingTest {      public static void main(String[] args) {          // Example of method overloading inward Java         Loan cheapLoan = Loan.createLoan("HSBC");         Loan veryCheapLoan = Loan.createLoan("Citibank", 8.5);          // Example of method overriding inward Java         Loan personalLoan = new PersonalLoan();         personalLoan.toString();     }  }  public class Loan {     private double interestRate;     private String customer;     private String lender;      public static Loan createLoan(String lender) {         Loan loan = new Loan();         loan.lender = lender;         return loan;     }      public static Loan createLoan(String lender, double interestRate) {         Loan loan = new Loan();         loan.lender = lender;         loan.interestRate = interestRate;         return loan;     }      @Override     public String toString() {         return "This is Loan past times Citibank";     }  }  public class PersonalLoan extends Loan {      @Override     public String toString() {         return "This is Personal Loan past times Citibank";     } }

Things to Remember

1) In instance of method overloading method signature gets changed piece inward instance of overriding signature remains same.

2) Return type is non component of method signature inward Java.

3) Overloaded method tin hold upwardly plain of report to compile fourth dimension binding but overridden method tin alone hold upwardly bind at run-time.

4) Both overloaded in addition to overridden method has same mention inward Java.

5) Static method tin non hold upwardly overridden inward Java.

6) Since individual method is too non visible exterior of class, it tin non hold upwardly overridden in addition to method binding happens during compile time.

7) From Java v onwards you lot tin role notation inward Java to declare overridden method just similar nosotros did amongst @override. @override notation allows compiler, IDE similar NetBeans and Eclipse to cross verify or banking concern check if this method is actually overrides super shape method or not.

Covariant Method Overriding inward Java

One of my reader Rajeev makes an interesting comment close i modify related to provide type of overriding method from Java v onwards, which enable to role subtype of provide type of overridden method. This is actually useful, when original method returns a full general type similar java.lang.Object. If you lot are overriding clone() method inward Java in addition to then you lot tin role this characteristic to provide actual type, instead of returning java.lang.Object in addition to tin relieve caller from type-casting cloned object. Here is the actual comment from Rajeev:


Hi Javin,I see your weblog regularly in addition to I constitute that you lot missed covariant return which is added inward Java v inward the instance of method overriding. When a subclass wants to modify the method implementation of an inherited method (an override), the subclass must define a method that matches the inherited version exactly. Or, equally of Java 5, you're allowed to modify the provide type inward the overriding method equally long equally the novel provide type is a subtype of the declared provide type of the overridden (super class) method. Let's expect at a covariant provide inward action:

class Alpha {     Alpha doStuff(char c) {         return new Alpha();     } }  class Beta extends Alpha {     Beta doStuff(char c) { // legal override inward Java 1.5         return new Beta();     } }

You tin meet that Beta shape which is overriding doStuff() method from Alpha shape is returning Beta type in addition to non Alpha type. This volition withdraw type casting on client side. See here to larn to a greater extent than close covariant method overriding inward Java.


AS I said i of the skilful illustration of this is overriding clone method in addition to using provide type equally Actual type instead of java.lang.Object, which is suggested past times Joshua Bloch inward Effective Java equally well. This inward in-fact i of the Java best practices piece implementing clone method inward Java. By the way don't forget to follow these Java overloading best practices, when doing it inward your project.

Further Learning
SOLID Principles of Object Oriented Design
Absolute Introduction to Object Oriented Programming inward Java
Java - Object Oriented Programming [For Absolute Beginners]

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