Difference Betwixt Method Overloading Together With Overriding Inward Java?

Method Overloading vs Method Overriding

Though the cite of the method remains same inwards the instance of both method overloading as well as overriding, nous departure comes from the fact that method overloading is resolved during compile time, spell method overriding is resolved at runtime. Also rules of overriding or overloading a method are unlike inwards Java. For example, a private, static as well as lastly method cannot live overriding inwards Java but you lot tin nevertheless overload them. For overriding both cite as well as signature of the method must rest same, but inwards for overloading method, the signature must live different. Last but non the to the lowest degree departure betwixt them is that telephone telephone to overloaded methods are resolved using static binding spell the telephone telephone to overridden method is resolved using dynamic binding inwards Java.

By the way, Method overloading as well as method overriding inwards Java is 2 of import concept inwards Java which allows Java programmer to declare method amongst same cite but unlike behavior. Method overloading as well as method overriding is based on Polymorphism inwards Java.

In instance of method overloading, method amongst same cite co-exists inwards same degree but they must possess got unlike method signature, spell inwards instance of method overriding, method amongst same cite is declared inwards derived degree or sub class.Method overloading is resolved using static binding inwards Java at compile fourth dimension spell method overriding is resolved using dynamic binding inwards Java at runtime.

In short, when you lot overload a method inwards Java its method signature got changed spell inwards instance of overriding method signature remains same but a method tin alone live overridden inwards sub class. Since Java supports Polymorphism as well as resolve object at run-time it is capable to telephone telephone overridden method inwards Java.

By the way departure betwixt method overloading as well as overriding is likewise ane of the pop Java blueprint question as well as appear inwards almost all levels of Java interviews.

What is method overloading as well as overriding inwards Java?

In this Java tutorial nosotros volition encounter how Java allows you lot to create 2 methods of same cite past times using method overloading as well as method overriding. We volition likewise affect base of operations on how methods are bonded or called past times Compiler as well as Java Virtual Machine as well as finally nosotros volition respond of pop interview questions departure betwixt method overloading as well as method overriding inwards Java.

This article is inwards my serial of Java article which discusses virtually Interview e.g. Difference betwixt Synchronized Collection as well as Concurrent Collection or How to Stop Thread inwards Java. Please allow me know if you lot possess got another interview questions as well as you lot are looking respond or argue for that as well as hither inwards nosotros volition effort to uncovering as well as speak over those interview questions.

How to Overload a Method inwards Java

If you lot possess got 2 methods amongst same cite inwards ane Java degree amongst unlike method signature than its called overloaded method inwards Java. Generally overloaded method inwards Java has unlike ready of arguments to perform something based on unlike release of input.

You tin likewise overload constructor inwards Java, which nosotros volition encounter inwards next instance of method overloading inwards Java. Binding of overloading method occurs during compile fourth dimension as well as overloaded calls resolved using static binding. To overload a Java method just changes its signature.

Just think inwards social club to alter signature you lot either demand to alter release of argument, type of declaration or social club of declaration inwards Java if they are of unlike types. Since furnish type is non component of method signature only changing furnish type volition lawsuit inwards duplicate method as well as you lot volition acquire compile fourth dimension mistake inwards Java.

In our instance of Loan as well as PersonalLoan class, createLoan method is overloaded. Since you lot possess got 2 crateLoan() method amongst ane takes ane declaration lender spell other possess got 2 declaration both lender as well as interestRate. Remember you lot tin overload static method inwards Java, you lot tin likewise overload individual as well as final method inwards Java but you lot tin non override them.

How to Override a Method inwards Java

In social club to override a Java method, you lot demand to create a nestling degree which extends parent. Overridden method inwards Java likewise shares same cite equally master copy method inwards Java but tin alone live overridden inwards sub class. Original method has to live defined within interface or base of operations class, which tin live abstract as well. When you lot override a method inwards Java its signature remains just same including furnish type. JVM resolves right overridden method based upon object at run-time past times using dynamic binding inwards Java. For instance inwards our instance when nosotros telephone telephone personalLoan.toString() method fifty-fifty though personalLoan object is of type Loan actual method called would live from PersonalLoan degree because object referenced past times personalLoan variable is of type PersonalLoan(). This is rattling useful technique to modify demeanor of a business office inwards Java based on unlike implementation. equals(), hashcode() as well as compareTo() methods are classic instance of overridden methods inwards Java.

Another of import indicate is that you lot tin non override static method inwards Java because they are associated amongst Class rather than object as well as resolved as well as bonded during compile fourth dimension as well as that’s the argue you lot cannot override nous method inwards Java. Similar to static, individual as well as lastly methods are likewise non overridden inwards Java. By the way, equally component of overriding best practice, e'er use @Override annotation, spell overriding method from an abstract degree or interface.

Rules of Method Overriding inwards Java

Following are rules of method overriding inwards coffee which must live followed spell overriding whatever method. As stated before private, static as well as final method tin non live overridden inwards Java. 

1. Method signature must live same including furnish type, release of method parameters, type of parameters as well as social club of parameters 
2. Overriding method tin non throw higher Exception than master copy or overridden method. way if master copy method throws IOException than overriding method tin non throw super degree of IOException e.g. Exception but it tin throw whatever sub degree of IOException or only does non throw whatever Exception. This dominion alone applies to checked Exception inwards Java, overridden method is gratis to throw whatever unchecked Exception. 
3. Overriding method tin non trim back accessibility of overridden method , way if master copy or overridden method is world than overriding method tin non arrive protected. 

Difference betwixt Method Overloading vs Overriding inwards Java

Overloading vs Overriding inwards Java is ane of the popular coffee interview questions at many companies as well as asked at unlike levels of programmers. Here are approximately of import departure betwixt overloading as well as overriding inwards Java. Though It's to a greater extent than of import is to empathise how to piece of occupation both overloading as well as overriding, these departure are practiced from interview perspective as well as gives approximately basic thought equally well:

1) First as well as most of import departure betwixt method overloading as well as overriding is that, In instance of method overloading inwards Java, signature of method changes spell inwards instance of method overriding it rest same.

2) Second major departure betwixt method overloading vs overriding inwards Java is that You tin overload method inwards ane degree but overriding tin alone live done on subclass.

3) You tin non override static, final as well as private method inwards Java but you lot tin overload static, lastly or individual method inwards Java.

4) Overloaded method inwards Java is bonded past times static binding as well as overridden methods are dependent champaign to dynamic binding.

5) Private as well as lastly method tin likewise live non overridden inwards Java.

By the way, you lot mightiness possess got heard virtually "a motion-picture present is worth to a greater extent than than thou words" as well as this is made truthful past times next image. By looking at the pic you lot tin clearly empathise departure betwixt method overloading as well as overriding inwards Java. 

Handling Exception spell overloading as well as overriding method inwards Java

While overriding a method it tin alone throw checked exception declared past times by overridden method or whatever subclass of it, way 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 inwards Java doesn't possess got such restriction as well as you lot are gratis to modify throws clause equally per your need.

Method Overloading as well as Overriding Example inwards Java

Here is an instance of both method overloading as well as method overriding inwards Java. In social club to explicate the concept nosotros possess got create 2 classes Loan and PersonalLoan. createLoan() method is overloaded equally it has unlike version amongst unlike signature, spell toString() method which is master copy declared inwards Object degree is overridden inwards both Loan as well as PersonalLoan class.

public class OverloadingOverridingTest {      public static void main(String[] args) {          // Example of method overloading inwards Java         Loan cheapLoan = Loan.createLoan("HSBC");         Loan veryCheapLoan = Loan.createLoan("Citibank", 8.5);          // Example of method overriding inwards 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 spell inwards instance of overriding signature remains same.

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

3) Overloaded method tin live dependent champaign to compile fourth dimension binding but overridden method tin alone live bind at run-time.

4) Both overloaded as well as overridden method has same cite inwards Java.

5) Static method tin non live overridden inwards Java.

6) Since individual method is likewise non visible exterior of class, it tin non live overridden as well as method binding happens during compile time.

7) From Java five onwards you lot tin piece of occupation notation inwards Java to declare overridden method just similar nosotros did amongst @override. @override notation allows compiler, IDE similar NetBeans and Eclipse to cross verify or cheque if this method is actually overrides super degree method or not.

Covariant Method Overriding inwards Java

One of my reader Rajeev makes an interesting comment virtually ane alter related to furnish type of overriding method from Java five onwards, which enable to piece of occupation subtype of furnish type of overridden method. This is actually useful, when master copy method returns a full general type similar java.lang.Object. If you lot are overriding clone() method inwards Java hence you lot tin piece of occupation this characteristic to furnish actual type, instead of returning java.lang.Object as well as tin relieve caller from type-casting cloned object. Here is the actual comment from Rajeev:


Hi Javin,I see your weblog regularly as well as I works life that you lot missed covariant return which is added inwards Java five inwards the instance of method overriding. When a subclass wants to alter 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 alter the furnish type inwards the overriding method equally long equally the novel furnish type is a subtype of the declared furnish type of the overridden (super class) method. Let's await at a covariant furnish inwards action:

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

You tin encounter that Beta degree which is overriding doStuff() method from Alpha degree is returning Beta type as well as non Alpha type. This volition take type casting on client side. See here to larn to a greater extent than virtually covariant method overriding inwards Java.


AS I said ane of the practiced instance of this is overriding clone method as well as using furnish type equally Actual type instead of java.lang.Object, which is suggested past times Joshua Bloch inwards Effective Java equally well. This inwards in-fact ane of the Java best practices spell implementing clone method inwards Java. By the way don't forget to follow these Java overloading best practices, when doing it inwards your project.

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

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