Polymorphism in Java with Examples in 2024- Great Learning

What’s Polymorphism in Java?

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

So, languages that don’t help polymorphism will not be ‘Object-Oriented Languages’, however ‘Object-Based mostly Languages’. Ada, for example, is one such language. Since Java helps polymorphism, it’s an Object-Oriented Language.

Polymorphism happens when there may be inheritance, i.e., many courses are associated.

Inheritance is a strong 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 totally different duties. Thus, permitting us to realize the identical motion in many various methods.

What’s Polymorphism?

The derivation of the phrase Polymorphism is from two totally different Greek words- poly and morphs. “Poly” means quite a few, and “Morphs” means types. So, polymorphism means innumerable types. Polymorphism, subsequently, is among the most vital options of Object-Oriented Programming.

Actual-Life Examples of Polymorphism

A person can have totally different relationships with totally different individuals. A girl could be a mom, a daughter, a sister, and a buddy, all on the identical time, i.e. she performs different behaviors in several conditions.

The human physique has totally different organs. Each organ has a distinct perform to carry out; the guts is liable for blood circulation, the lungs for respiratory, the mind for cognitive exercise, and the kidneys for excretion. So now we have an ordinary methodology perform that performs otherwise relying upon the organ of the physique. 

Polymorphism in Java Instance

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

class Shapes {
  public void space() {
    System.out.println("The method 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 Predominant {
  public static void predominant(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 method for the realm of the Triangle is ½ * base * top
The method 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 Predominant {
    public static void predominant(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 predominant methodology, we create two situations of the Form class, s1 and s2, which are literally situations of the Circle and Sq. subclasses. Once we name the draw() methodology on these objects, the proper implementation known as based mostly on the precise sort of the article, 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 permits 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 sort of the article and calls the corresponding methodology.

Additionally Learn: OOPs concepts in Java

Forms of Polymorphism

You’ll be able to carry out Polymorphism in Java through two totally 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 title in the identical class, and all of the strategies work in several methods. Methodology overloading happens when there may be multiple methodology of the identical title 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 Predominant {
  public static void predominant(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 father or mother class.

Instance of Methodology Overriding in Java

class Automobile{  
  //defining a technique  
  void run(){System.out.println("Automobile is transferring");}  
}  
//Creating a toddler class  
class Car2 extends Automobile{  
  //defining the identical methodology as within the father or mother class  
  void run(){System.out.println("automotive is operating safely");}  
  
  public static void predominant(String args[]){  
  Car2 obj = new Car2();//creating object  
  obj.run();//calling methodology  
  }  
}  

Output:

Automobile is operating safely

Additionally, Polymorphism in Java will be categorised into two sorts, i.e:

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

What’s Compile-Time Polymorphism in Java?

Compile Time Polymorphism In Java is often known as Static Polymorphism. Moreover, the decision to the tactic is resolved at compile-time. Compile-Time polymorphism is achieved by means of Methodology Overloading. This kind of polymorphism will also be achieved by means of Operator Overloading. Nevertheless, Java doesn’t help Operator Overloading.

Methodology Overloading is when a category has a number of strategies with the identical title, however the quantity, sorts, and order of parameters and the return sort of the strategies are totally different. Java permits the consumer freedom to make use of the identical title for numerous capabilities so long as it may distinguish between them by the sort 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’ll 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 predominant(String[] args) 
{ 
Addition obj = new Addition(); 
obj.sum ( 30,90); 
obj.sum(45, 80, 22); 
} 
}

The output of this system can be: 

Sum of two numbers: 120 

Sum of three numbers: 147 

On this program, the sum() methodology overloads with two sorts through totally different parameters. 

That is the essential idea of compile-time polymorphism in java the place we will carry out numerous operations by utilizing a number of strategies having the identical title.

What’s Runtime Polymorphism in Java?

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

Methodology Overriding is finished when a toddler or a subclass has a technique with the identical title, parameters, and return sort because the father or mother or the superclass; then that perform overrides the perform within the superclass. In less complicated phrases, if the subclass gives its definition to a technique already current within the superclass; then that perform within the base class is claimed to be overridden.

Additionally, it ought to be famous that runtime polymorphism can solely be achieved by means of capabilities and never knowledge members. 

Overriding is finished by utilizing a reference variable of the superclass. The tactic to be referred to as is decided based mostly on the article which is being referred to by the reference variable. That is often known as Upcasting.

Upcasting takes place when the Mother or father 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 lengthen the superclass and override its eat() methodology. We’ll name the eat() methodology by the reference variable of Mother or father 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 Vegetation");
} 
  }
class omnivores extends Animal{  
  void eat(){
System.out.println("Omnivores Eat Vegetation and meat");
} 
  }
class carnivores extends Animal{  
  void eat(){
System.out.println("Carnivores Eat meat");
} 
  }
class predominant{
  public static void predominant(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 Vegetation
Omnivores Eat Vegetation and meat
Carnivores eat meat

Instance 2:

On this instance, we’re creating one superclass Hillstations and three subclasses Manali, Mussoorie, Gulmarg. Subclasses lengthen the superclass and override its location() and famousfor() methodology. We’ll name the situation() and famousfor() methodology by the Mother or father 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 schooling establishments");
}  
  }
class Gulmarg extends Hillstations {  
  void location(){
System.out.println("Gulmarg is in J&Okay");
}  
void famousfor(){
System.out.println("It's Well-known for snowboarding");
}  
  }
class predominant{
  public static void predominant(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 schooling establishments
Gulmarg is in J&Okay
It’s Well-known for snowboarding

Instance of run-time polymorphism in java

We’ll create two courses Automobile and Innova, Innova class will lengthen the automotive class and can override its run() methodology.

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

The output of the next program can be; 

Working quick at 120 km. 

One other instance for run-time polymorphism in Java

Now, allow us to examine if we will obtain runtime polymorphism through knowledge members. 

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

The output of the next program can be : 

125 

This clearly implies we will’t obtain Runtime polymorphism through knowledge members. Briefly, a technique is overridden, not the info 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 predominant(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 can 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 Predominant 
{ 
public static void predominant(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 can be; 

The buffalo sound- gho,gho 

The snake sound- his,his 

The tiger sound- roooo,roooo 

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

Polymorphic Subtypes

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

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

Assuming now we have to attract some arbitrary shapes, we will introduce a category named ‘form’ with a draw() methodology. By overriding draw() with different subclasses comparable to circle, sq., rectangle, trapezium, and so forth we’ll introduce an array of sort ‘form’ whose components retailer references will seek advice from ‘form’ subclass references. Subsequent time, we’ll name draw(), all shapes situations draw () methodology can be referred to as.

This Subtype polymorphism typically depends on upcasting and late binding. A casting the place you solid 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 shouldn’t carry out any argument checks, sort checks, methodology calls, and so forth, and depart every little thing on the runtime. 

What’s Polymorphism in Programming?

Polymorphism in programming is outlined utilization of a single image to symbolize a number of differing types.

What’s Polymorphism Variables?

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

Why use Polymorphism in Java?

Polymorphism in Java makes it attainable to jot down a technique that may accurately course of plenty of various kinds of functionalities which have the identical title. We are able to additionally acquire consistency in our code by utilizing polymorphism.

Benefits of Polymorphism in Java

1. It gives reusability to the code. The courses which can be written, examined and carried out will be reused a number of occasions. Moreover, it saves numerous 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 will be modified with out altering that variable’s worth within the superclass; or another 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 sort of object into a brand new object of a distinct type. Additionally, that is achieved mechanically to forestall sort errors within the code. 

Programming languages comparable to C, java, and so forth help the conversion of worth from one knowledge sort to a different knowledge sort. Knowledge sort conversions are of two sorts, i.e., implicit and specific. 

Implicit sort conversion is mechanically achieved in this system and one of these 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 sort error.

Instance:

class coercion {

  public static void predominant(String[] args) {
    Double space = 3.14*5*7;
System.out.println(space);
String s = "comfortable";
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 help 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 alternative. Due to this fact, an operator image or methodology title can be utilized as a ‘user-defined’ sort as per the necessities. 

For instance, ‘+’ can be utilized to carry out the addition of numbers (identical knowledge sort) 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 predominant(String[] args) {
    
String s = "comfortable";
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 determine how the operator will interpret.

 3. Polymorphic Variables or Parameters

In Java, the article or occasion variables symbolize the polymorphic variables. It’s 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 sorts through the time of execution.

Parametric polymorphism specifies that whereas class declaration, a subject title can affiliate with differing types, and a technique title can affiliate with totally different parameters and return sorts.

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 Predominant{
public static void predominant(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’s because the superclass’s identical object refers back to the father or mother 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 sort of difficult whereas implementation.
• It tends to cut 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 sort or casting a standard sort to a person sort.

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 slender the kind of objects, which suggests we’re changing frequent sort to particular person sort. 

Vegetable vegetable = new Tomato(); 

Tomato castedTomato = (Tomato) vegetable; 

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

We explicitly inform the compiler what the runtime sort of the article is.

Fragile base class downside 

Fragile base class downside is nothing however a basic architectural downside. 

Typically the improper design of a father or mother 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 standards is met. 

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

Mainly, the explanation for the delicate base downside is that the developer of the bottom class has no concept of the subclass design. There isn’t any resolution but for this downside. 

Conclusion

We hope you could have gotten a fundamental concept of polymorphism in Java and the way we use it in addition to issues associated to them. 

Therefore, this brings us to the tip of the weblog on Polymorphism in Java. Moreover, to study extra about programming and different associated ideas, take a look at the programs on Great Learning Academy and PG Programs in Software Engineering.  

Additionally, in case you are getting ready for Interviews, take a look at these Interview Questions for Java to ace it like a professional.

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

Steadily Requested Questions

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