Method Overloading In Java + Compile Time Polymorphism In Java

Hi All,

Greetings of the day.

Today we will explore method overloading in java.

Method Overloading - Method overloading allows the user to define a method with the same name but with different parameters and optionally with the different return types.

Rules for method overloading

The overloaded method must change arguments.
The return type can change but it's optional.
The overloaded method can throw any new checked/unchecked exception, or broader checked exceptions.
We can change the access specifier in method overloading.

Compile Time Polymorphism / Invoking Overloaded Method

With method overloading we can have multiple methods with the same name, so which overloaded method will be invoked is decided at compile-time based on object reference and no of arguments.

So let's take an example

package com.demo;

public class Vehicle {

}

Now Car will extend Vehicle

package com.demo;

public class Car extends Vehicle{

}

Now we will create instances of Vehicle & Car and explore why method overloading is compile-time polymorphism.

package com.demo;

public class Test {

	public void driveVehicle(Vehicle vehicle) {
		System.out.println("Drive vehicle called for vehicle...");
	}
	
	public void driveVehicle(Car car) {
		System.out.println("Drive vehicle called for car...");
	}
	
	public static void main(String[] args) {
		
		Test test=new Test();
		Vehicle vehicle=new Vehicle();
		Car car=new Car();
		
		Vehicle vehicle2=new Car();
		
		test.driveVehicle(vehicle);
		test.driveVehicle(car);
		test.driveVehicle(vehicle2);
	}
}

O/P

Drive vehicle called for vehicle...
Drive vehicle called for car...
Drive vehicle called for vehicle...

Take look on

Vehicle vehicle2=new Car();

test.driveVehicle(vehicle2);

Here at run time vehicle2 is pointing to instance is of Car but still, we get output as Drive vehicle called for vehicle... because which overloaded method will be called is decided at compile-time based on object reference which is of Vehicle type so driveVehicle method with Vehicle as an argument is called.

Let me know if you have any questions.

Also, you can refer below useful post

Method Overriding In Java + Runtime Polymorphism In Java

Static And Instance Initialization Block In Java

Comparator and Comparable In Java + Difference Between Comparator and Comparable + Java 8

Java 8 Stream - Intermediate Operations With Examples

Java 8 Stream - Terminal Operations With Examples

For Spring visit Spring Tutorial

Thanks

Happy Learning !!