Polymorphism in Java with Examples in 2024- Nice Studying

What’s Polymorphism in Java?

Polymorphism in Java is the duty that performs a single motion in numerous methods.

So, languages that don’t assist polymorphism aren’t ‘Object-Oriented Languages’, however ‘Object-Primarily based Languages’. Ada, for example, is one such language. Since Java helps polymorphism, it’s an Object-Oriented Language.

Polymorphism happens when there’s inheritance, i.e., many courses are associated.

Inheritance is a robust characteristic in Java. Java Inheritance lets one class purchase the properties and attributes of one other class. Polymorphism in Java permits us to make use of these inherited properties to carry out completely different duties. Thus, permitting us to attain the identical motion in many various methods.

What’s Polymorphism?

The derivation of the phrase Polymorphism is from two completely different Greek words- poly and morphs. “Poly” means quite a few, and “Morphs” means kinds. So, polymorphism means innumerable kinds. Polymorphism, subsequently, is without doubt one of the most vital options of Object-Oriented Programming.

Actual-Life Examples of Polymorphism

A person can have completely different relationships with completely different folks. A girl is usually a mom, a daughter, a sister, and a pal, all on the similar time, i.e. she performs different behaviors in numerous conditions.

The human physique has completely different organs. Each organ has a unique operate to carry out; the center is accountable for blood move, the lungs for respiration, the mind for cognitive exercise, and the kidneys for excretion. So now we have a typical methodology operate that performs in another way relying upon the organ of the physique. 

Polymorphism in Java Instance

A superclass named “Shapes” has a way referred to as “space()”. Subclasses of “Shapes” could be “Triangle”, “circle”, “Rectangle”, and so on. Every subclass has its method of calculating space. Utilizing Inheritance and Polymorphism means, the subclasses can use the “space()” methodology to seek out the realm’s components for that form.

class Shapes {
  public void space() {
    System.out.println("The components for space of ");
  }
}
class Triangle extends Shapes {
  public void space() {
    System.out.println("Triangle is ½ * base * top ");
  }
}
class Circle extends Shapes {
  public void space() {
    System.out.println("Circle is 3.14 * radius * radius ");
  }
}
class Principal {
  public static void foremost(String[] args) {
    Shapes myShape = new Shapes();  // Create a Shapes object
    Shapes myTriangle = new Triangle();  // Create a Triangle object
    Shapes myCircle = new Circle();  // Create a Circle object
    myShape.space();
    myTriangle.space();
    myShape.space();
    myCircle.space();
  }
}

Output:

The components for the realm of the Triangle is ½ * base * top
The components for the realm of the Circle is 3.14 * radius * radius

class Form {
    public void draw() {
        System.out.println("Drawing a form");
    }
}

class Circle extends Form {
    @Override
    public void draw() {
        System.out.println("Drawing a circle");
    }
}

class Sq. extends Form {
    @Override
    public void draw() {
        System.out.println("Drawing a sq.");
    }
}

class Principal {
    public static void foremost(String[] args) {
        Form s1 = new Circle();
        Form s2 = new Sq.();

        s1.draw(); // Output: "Drawing a circle"
        s2.draw(); // Output: "Drawing a sq."
    }
}

On this instance, now we have a base class Form with a single methodology draw() that prints “Drawing a form” to the console. We then create two subclasses, Circle and Sq., that override the draw() methodology to print “Drawing a circle” and “Drawing a sq.” respectively.

Within the foremost methodology, we create two situations of the Form class, s1 and s2, which are literally situations of the Circle and Sq. subclasses. After we name the draw() methodology on these objects, the proper implementation is named based mostly on the precise kind of the item, that is run-time polymorphism. This system will output: “Drawing a circle” and “Drawing a sq.”

On this instance, the draw() methodology is overridden within the subclasses, and this enables for this system to find out which methodology to make use of at runtime. This is called runtime polymorphism or dynamic polymorphism, As a result of at runtime the JVM determines the precise kind of the item and calls the corresponding methodology.

Additionally Learn: OOPs ideas in Java

Forms of Polymorphism

You’ll be able to carry out Polymorphism in Java by way of two completely different strategies:

1. Methodology Overloading
2. Methodology Overriding

What’s Methodology Overloading in Java?

Methodology overloading is the method that may create a number of strategies of the identical identify in the identical class, and all of the strategies work in numerous methods. Methodology overloading happens when there’s a couple of methodology of the identical identify within the class.

Instance of Methodology Overloading in Java

class Shapes {
  public void space() {
    System.out.println("Discover space ");
  }
public void space(int r) {
    System.out.println("Circle space = "+3.14*r*r);
  }

public void space(double b, double h) {
    System.out.println("Triangle space="+0.5*b*h);
  }
public void space(int l, int b) {
    System.out.println("Rectangle space="+l*b);
  }


}

class Principal {
  public static void foremost(String[] args) {
    Shapes myShape = new Shapes();  // Create a Shapes object
    
    myShape.space();
    myShape.space(5);
    myShape.space(6.0,1.2);
    myShape.space(6,2);
    
  }
}

Output:

Discover space
Circle space = 78.5
Triangle space=3.60
Rectangle space=12

What’s Methodology Overriding in Java?

Methodology overriding is the method when the subclass or a toddler class has the identical methodology as declared within the dad or mum class.

Instance of Methodology Overriding in Java

class Car{  
  //defining a way  
  void run(){System.out.println("Car is shifting");}  
}  
//Creating a toddler class  
class Car2 extends Car{  
  //defining the identical methodology as within the dad or mum class  
  void run(){System.out.println("automobile is working safely");}  
  
  public static void foremost(String args[]){  
  Car2 obj = new Car2();//creating object  
  obj.run();//calling methodology  
  }  
}  

Output:

Automobile is working safely

Additionally, Polymorphism in Java could be categorised into two varieties, i.e:

1. Static/Compile-Time Polymorphism
2. Dynamic/Runtime Polymorphism

What’s Compile-Time Polymorphism in Java?

Compile Time Polymorphism In Java is also referred to as Static Polymorphism. Moreover, the decision to the strategy is resolved at compile-time. Compile-Time polymorphism is achieved by way of Methodology Overloading. This sort of polymorphism can be achieved by way of Operator Overloading. Nevertheless, Java doesn’t assist Operator Overloading.

Methodology Overloading is when a category has a number of strategies with the identical identify, however the quantity, varieties, and order of parameters and the return kind of the strategies are completely different. Java permits the consumer freedom to make use of the identical identify for varied features so long as it might probably distinguish between them by the kind and variety of parameters. Take a look at among the vital questions on run time polymorphism in java interview questions.

Instance of Compile-Time Polymorphism in Java

We are going to do addition in Java and perceive the idea of compile time polymorphism utilizing subtract() 

bundle staticPolymorphism; 
public class Addition 
{ 
void sum(int a, int b) 
{ 
int c = a+b; 
System.out.println(“ Addition of two numbers :” +c); } 
void sum(int a, int b, int e) 
{ 
int c = a+b+e; 
System.out.println(“ Addition of three numbers :” +c); } 
public static void foremost(String[] args) 
{ 
Addition obj = new Addition(); 
obj.sum ( 30,90); 
obj.sum(45, 80, 22); 
} 
}

The output of this system shall be: 

Sum of two numbers: 120 

Sum of three numbers: 147 

On this program, the sum() methodology overloads with two varieties by way of completely different parameters. 

That is the essential idea of compile-time polymorphism in java the place we are able to carry out varied operations through the use of a number of strategies having the identical identify.

What’s Runtime Polymorphism in Java?

Runtime polymorphism in Java can also be popularly generally known as Dynamic Binding or Dynamic Methodology Dispatch. On this course of, the decision to an overridden methodology is resolved dynamically at runtime moderately than at compile-time. You’ll be able to obtain Runtime polymorphism by way of Methodology Overriding.

Methodology Overriding is finished when a toddler or a subclass has a way with the identical identify, parameters, and return kind because the dad or mum or the superclass; then that operate overrides the operate within the superclass. In less complicated phrases, if the subclass supplies its definition to a way already current within the superclass; then that operate within the base class is alleged to be overridden.

Additionally, it must be famous that runtime polymorphism can solely be achieved by way of features and never knowledge members. 

Overriding is finished through the use of a reference variable of the superclass. The strategy to be referred to as is decided based mostly on the item which is being referred to by the reference variable. That is also referred to as Upcasting.

Upcasting takes place when the Mum or dad class’s reference variable refers back to the object of the kid class. For instance:

class A{} 
class B extends A{}  
A a=new B(); //upcasting

Examples of Runtime Polymorphism in Java

Instance 1:

On this instance, we’re creating one superclass Animal and three subclasses, Herbivores, Carnivores, and Omnivores. Subclasses prolong the superclass and override its eat() methodology. We are going to name the eat() methodology by the reference variable of Mum or dad class, i.e. Animal class. Because it refers back to the base class object and the bottom class methodology overrides the superclass methodology; the bottom class methodology is invoked at runtime. As Java Digital Machine or the JVM and never the compiler determines methodology invocation, it’s, subsequently, runtime polymorphism.

class Animal{  
  void eat(){
System.out.println("Animals Eat");
}  
}  
class herbivores extends Animal{  
  void eat(){
System.out.println("Herbivores Eat Crops");
} 
  }
class omnivores extends Animal{  
  void eat(){
System.out.println("Omnivores Eat Crops and meat");
} 
  }
class carnivores extends Animal{  
  void eat(){
System.out.println("Carnivores Eat meat");
} 
  }
class foremost{
  public static void foremost(String args[]){ 
    Animal A = new Animal();
    Animal h = new herbivores(); //upcasting  
	Animal o = new omnivores(); //upcasting  
    Animal c = new carnivores(); //upcasting  
    A.eat();
    h.eat();
    o.eat();  
    c.eat();  
  
  }  
}  

Output:

Animals eat
Herbivores Eat Crops
Omnivores Eat Crops and meat
Carnivores eat meat

Instance 2:

On this instance, we’re creating one superclass Hillstations and three subclasses Manali, Mussoorie, Gulmarg. Subclasses prolong the superclass and override its location() and famousfor() methodology. We are going to name the placement() and famousfor() methodology by the Mum or dad class’, i.e. Hillstations class. Because it refers back to the base class object and the bottom class methodology overrides the superclass methodology; the bottom class methodology is invoked at runtime. Additionally, as Java Digital Machine or the JVM and never the compiler determines methodology invocation, it’s runtime polymorphism.

class Hillstations{  
  void location(){
System.out.println("Location is:");
}  
void famousfor(){
System.out.println("Well-known for:");
}  

}  
class Manali extends Hillstations {  
  void location(){
System.out.println("Manali is in Himachal Pradesh");
}  
void famousfor(){
System.out.println("It's Well-known for Hadimba Temple and journey sports activities");
}  
  }
class Mussoorie extends Hillstations {  
  void location(){
System.out.println("Mussoorie is in Uttarakhand");
}  
void famousfor(){
System.out.println("It's Well-known for training establishments");
}  
  }
class Gulmarg extends Hillstations {  
  void location(){
System.out.println("Gulmarg is in J&Ok");
}  
void famousfor(){
System.out.println("It's Well-known for snowboarding");
}  
  }
class foremost{
  public static void foremost(String args[]){ 
    Hillstations A = new Hillstations();
    Hillstations M = new Manali();

    Hillstations Mu = new Mussoorie();

    Hillstations G = new Gulmarg();

    A.location();
A.famousfor();

M.location();
M.famousfor();

Mu.location();
Mu.famousfor();

G.location();
G.famousfor();
  }  
}  

Output:

Location is:
Well-known for:
Manali is in Himachal Pradesh
It’s Well-known for Hadimba Temple and journey sports activities
Mussoorie is in Uttarakhand
It’s Well-known for training establishments
Gulmarg is in J&Ok
It’s Well-known for snowboarding

Instance of run-time polymorphism in java

We are going to create two courses Automobile and Innova, Innova class will prolong the automobile class and can override its run() methodology.

class Automobile 
{ 
void run() 
{ 
System.out.println(“ working”); 
} 
}
class innova extends Automobile 
{ 
void run(); 
{ 
System.out.println(“ working quick at 120km”); 
} 
public static void foremost(String args[]) 
{ 
Automobile c = new innova(); 
c.run(); 
} 
} 

The output of the next program shall be; 

Operating quick at 120 km. 

One other instance for run-time polymorphism in Java

Now, allow us to verify if we are able to obtain runtime polymorphism by way of knowledge members. 

class automobile 
{ 
int speedlimit = 125; 
} 
class innova extends automobile 
{ 
int speedlimit = 135; 
public static void foremost(String args[]) 
{ 
automobile obj = new innova(); 
System.out.println(obj.speedlimit);
}

The output of the next program shall be : 

125 

This clearly implies we are able to’t obtain Runtime polymorphism by way of knowledge members. Briefly, a way is overridden, not the information members.

Runtime polymorphism with multilevel inheritance

class grandfather 
{ 
void swim() 
{ 
System.out.println(“ Swimming”); 
} 
} 
class father extends grandfather 
{ 
void swim() 
{ 
System.out.println(“ Swimming in river”); 
} 
} 
class son extends father 
{ 
void swim() 
{ 
System.out.println(“ Swimming in pool”);
} 
public static void foremost(String args[]) 
{ 
grandfather f1,f2,f3; 
f1 =new grandfather(); 
f2 = new father(); 
f3 = new son(); 
f1.swim(); 
f2.swim(); 
f3.swim(): 
} 
} 

The output of the next program shall be: 

Swimming, Swimming in river, Swimming in pool

One other runtime polymorphism with multilevel inheritance instance

class soundAnimal 
{ 
public void Sound() 
{ 
System.out.println("Totally different sounds of animal"); }
} 
class buffalo extends soundAnimal 
{ 
public void Sound() 
{ 
System.out.println("The buffalo sound- gho,gho"); } 
} 
class snake extends soundAnimal 
{ 
public void Sound() 
{ 
System.out.println("The snake sound- his,his"); } 
} 
class tiger extends soundAnimal
{ 
public void Sound() 
{ 
System.out.println("The tiger sounds- roooo, rooo"); } 
} 
public class Animal Principal 
{ 
public static void foremost(String[] args) 
{ 
soundAnimal Animal = new soundAnimal(); soundAnimal buffalo = new buffalo(); 
soundAnimal snake = new snake(); 
soundAnimal tiger = new tiger(); 
Animal.Sound(); 
buffalo.Sound();
snake.Sound(); 
tiger.Sound(); 
} 
} 

The output of the next program shall be; 

The buffalo sound- gho,gho 

The snake sound- his,his 

The tiger sound- roooo,roooo 

We hope you bought an thought about runtime and compile-time polymorphism.

Polymorphic Subtypes

Subtype mainly signifies that a subtype can function one other kind’s subtype, sounds a bit sophisticated? 

Let’s perceive this with the assistance of an instance:

Assuming now we have to attract some arbitrary shapes, we are able to introduce a category named ‘form’ with a draw() methodology. By overriding draw() with different subclasses similar to circle, sq., rectangle, trapezium, and so on we are going to introduce an array of kind ‘form’ whose parts retailer references will consult with ‘form’ subclass references. Subsequent time, we are going to name draw(), all shapes situations draw () methodology shall be referred to as.

This Subtype polymorphism usually depends on upcasting and late binding. A casting the place you forged up the inheritance hierarchy from subtype to a supertype is termed upcasting.

To name non-final occasion strategies we use late binding. Briefly, a compiler mustn’t carry out any argument checks, kind checks, methodology calls, and so on, and depart every little thing on the runtime. 

What’s Polymorphism in Programming?

Polymorphism in programming is outlined utilization of a single image to characterize a number of differing kinds.

What’s Polymorphism Variables?

A polymorphic variable is outlined as a variable that may maintain values of various varieties in the course of the course of execution.

Why use Polymorphism in Java?

Polymorphism in Java makes it attainable to put in writing a way that may appropriately course of plenty of several types of functionalities which have the identical identify. We are able to additionally acquire consistency in our code through the use of polymorphism.

Benefits of Polymorphism in Java

1. It supplies reusability to the code. The courses which are written, examined and applied could be reused a number of instances. Moreover, it saves a number of time for the coder. Additionally, the one can change the code with out affecting the unique code.
2. A single variable can be utilized to retailer a number of knowledge values. The worth of a variable you inherit from the superclass into the subclass could be modified with out altering that variable’s worth within the superclass; or some other subclasses.
3. With lesser strains of code, it turns into simpler for the programmer to debug the code.

Traits of Polymorphism

Polymorphism has many different traits apart from Methodology Overloading and Methodology Overriding. They embrace:

• Coercion
• Inside Operator Overloading
• Polymorphic Variables or Parameters

1. Coercion

Coercion offers with implicitly changing one kind of object into a brand new object of a unique sort. Additionally, that is completed robotically to forestall kind errors within the code. 

Programming languages similar to C, java, and so on assist the conversion of worth from one knowledge kind to a different knowledge kind. Knowledge kind conversions are of two varieties, i.e., implicit and express. 

Implicit kind conversion is robotically completed in this system and the sort of conversion can also be termed coercion. 

For instance, if an operand is an integer and one other one is in float, the compiler implicitly converts the integer into float worth to keep away from kind error.

Instance:

class coercion {

  public static void foremost(String[] args) {
    Double space = 3.14*5*7;
System.out.println(space);
String s = "completely happy";
int x=5;
String phrase = s+x;
System.out.println(phrase);

  }
}

Output:

109.9
happy5

2. Inside Operator Overloading

In Operator Overloading, an operator or image behaves in additional methods than one relying upon the enter context or the kind of operands. It’s a attribute of static polymorphism. Though Java doesn’t assist user-defined operator overloading like C++, the place the consumer can outline how an operator works for various operands, there are few situations the place Java internally overloads operators.

Operator overloading is the idea of utilizing the operator as per your selection. Due to this fact, an operator image or methodology identify can be utilized as a ‘user-defined’ kind as per the necessities. 

For instance, ‘+’ can be utilized to carry out the addition of numbers (similar knowledge kind) or for concatenation of two or extra strings.

Within the case of +, can be utilized for addition and likewise for concatenation.

For instance:

class coercion {

  public static void foremost(String[] args) {
    
String s = "completely happy";
String s1 = "world";
int x=5;
int y=10;

System.out.println(s+s1);
System.out.println(x+y);

  }
}

Output :

Equally, operators like! &, and | are additionally within the overload place for logical and bitwise operations. In each of those instances, the kind of argument will resolve how the operator will interpret.

 3. Polymorphic Variables or Parameters

In Java, the item or occasion variables characterize the polymorphic variables. It is because any object variables of a category can have an IS-A relationship with their very own courses and subclasses.

The Polymorphic Variable is a variable that may maintain values of various varieties in the course of the time of execution.

Parametric polymorphism specifies that whereas class declaration, a subject identify can affiliate with differing kinds, and a way identify can affiliate with completely different parameters and return varieties.

For instance:

class Form
{
public void show()
{
System.out.println("A Form.");
}
}
class Triangle extends Form
{
public void show()
{
System.out.println("I'm a triangle.");
}
}
class Principal{
public static void foremost(String[] args)
{
Form obj;
obj = new Form();
obj.show();
obj = new Triangle();
obj.show();
}
}

Output:

A Form.
I’m a triangle.

Right here, the obj object is a polymorphic variable. It is because the superclass’s similar object refers back to the dad or mum class (Form) and the kid class (Triangle). 

Issues with Polymorphism 

With plenty of benefits, there are additionally just a few disadvantages of polymorphism.

• Polymorphism is kind of difficult whereas implementation.
• It tends to scale back the readability of the code.
• It raises some critical efficiency points in real-time as nicely.

Sort Identification Throughout Downcasting 

Downcasting is termed as casting to a toddler kind or casting a standard kind to a person kind.

So, we use downcasting each time we have to entry or perceive the behaviour of the subtypes. 

Instance, 

It is a hierarchical instance 

Meals> Vegetable> Ladyfinger, Tomato 

Right here, tomato and ladyfinger are two subclasses. 

In downcasting, we slim the kind of objects, which suggests we’re changing widespread kind to particular person kind. 

Vegetable vegetable = new Tomato(); 

Tomato castedTomato = (Tomato) vegetable; 

Right here we’re casting widespread kind to a person kind, superclass to subclass which isn’t attainable immediately in java.

We explicitly inform the compiler what the runtime kind of the item is.

Fragile base class drawback 

Fragile base class drawback is nothing however a elementary architectural drawback. 

Typically the improper design of a dad or mum class can lead a subclass of a superclass to make use of superclass in some unpredicted methods. 

The fragility of inheritance will result in damaged codes even when all the factors is met. 

This architectural drawback is termed as a fragile base class drawback in object-oriented programming programs and language. 

Principally, the explanation for the delicate base drawback is that the developer of the bottom class has no thought of the subclass design. There isn’t a answer but for this drawback. 

Conclusion

We hope you should have gotten a primary thought of polymorphism in Java and the way we use it in addition to issues associated to them. 

Therefore, this brings us to the top of the weblog on Polymorphism in Java. Moreover, to be taught extra about programming and different associated ideas, try the programs on Nice Studying Academy and PG Applications in Software program Engineering.  

Additionally, if you’re making ready for Interviews, try these Interview Questions for Java to ace it like a professional.

So, don’t cease your journey of studying. Additionally, don’t overlook to upskill and reskill your self. Preserve exploring and continue learning.

Incessantly Requested Questions

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