Polymorphism in Java

Difficulty Level : Easy
Last Updated : 01 Dec, 2020

The word polymorphism means having many forms. In simple words, we can define polymorphism as the ability of a message to be displayed in more than one form.

Real life example of polymorphism: A person at the same time can have different characteristic. Like a man at the same time is a father, a husband, an employee. So the same person posses different behavior in different situations. This is called polymorphism.

Polymorphism is considered one of the important features of Object-Oriented Programming. Polymorphism allows us to perform a single action in different ways. In other words, polymorphism allows you to define one interface and have multiple implementations. The word “poly” means many and “morphs” means forms, So it means many forms.

In Java polymorphism is mainly divided into two types:

Compile time Polymorphism
Runtime Polymorphism

1. Compile-time polymorphism: It is also known as static polymorphism. This type of polymorphism is achieved by function overloading or operator overloading. But Java doesn’t support the Operator Overloading.

Method Overloading: When there are multiple functions with same name but different parameters then these functions are said to be overloaded. Functions can be overloaded by change in number of arguments or/and change in type of arguments.

Example: By using different types of arguments

// Java program for Method overloading 
  
class MultiplyFun { 
  
    // Method with 2 parameter 
    static int Multiply(int a, int b) 
    { 
        return a * b; 
    } 
  
    // Method with the same name but 2 double parameter 
    static double Multiply(double a, double b) 
    { 
        return a * b; 
    } 
} 
  
class Main { 
    public static void main(String[] args) 
    { 
  
        System.out.println(MultiplyFun.Multiply(2, 4)); 
  
        System.out.println(MultiplyFun.Multiply(5.5, 6.3)); 
    } 
} 

Output:

8
34.65

Example 2: By using different numbers of arguments

// Java program for Method overloading 
  
class MultiplyFun { 
  
    // Method with 2 parameter 
    static int Multiply(int a, int b) 
    { 
        return a * b; 
    } 
  
    // Method with the same name but 3 parameter 
    static int Multiply(int a, int b, int c) 
    { 
        return a * b * c; 
    } 
} 
  
class Main { 
    public static void main(String[] args) 
    { 
        System.out.println(MultiplyFun.Multiply(2, 4)); 
  
        System.out.println(MultiplyFun.Multiply(2, 7, 3)); 
    } 
} 

Output:

8
42

2. Runtime polymorphism: It is also known as Dynamic Method Dispatch. It is a process in which a function call to the overridden method is resolved at Runtime. This type of polymorphism is achieved by Method Overriding.

Method overriding, on the other hand, occurs when a derived class has a definition for one of the member functions of the base class. That base function is said to be overridden.

Example:

// Java program for Method overriding 
  
class Parent { 
  
    void Print() 
    { 
        System.out.println("parent class"); 
    } 
} 
  
class subclass1 extends Parent { 
  
    void Print() 
    { 
        System.out.println("subclass1"); 
    } 
} 
  
class subclass2 extends Parent { 
  
    void Print() 
    { 
        System.out.println("subclass2"); 
    } 
} 
  
class TestPolymorphism3 { 
    public static void main(String[] args) 
    { 
  
        Parent a; 
  
        a = new subclass1(); 
        a.Print(); 
  
        a = new subclass2(); 
        a.Print(); 
    } 
} 

Output:

subclass1
subclass2

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