Polymorphism in Java: Definition, Types, and Examples

Polymorphism in Java

Polymorphism is an object-oriented programming concept in which a single reference variable can exhibit different behaviors depending on the object it refers to.

Types of Polymorphism

Polymorphism in Java is classified into two types:

1. Compile-Time Polymorphism
2. Run-Time Polymorphism

1. Compile-Time Polymorphism

In compile-time polymorphism, the method resolution is performed by the compiler.

Key Points

• The compiler resolves the method call based on the parameter list.
• Once method resolution is done, the compiler performs static binding.
• In static binding:

              ✓ The method declaration is bound to the method definition at compile time.

• Compile-time polymorphism is achieved using method overloading.

Example

class Calculator {

    int add(int a, int b) {

        return a + b;

    }

    double add(double a, double b) {

        return a + b;

    }

}

2. Run-Time Polymorphism

In run-time polymorphism, the method resolution is performed by the JVM.

Key Points

• The JVM resolves the method call based on the object present inside the reference variable.
• Once method resolution is done, the JVM performs dynamic binding.
• In dynamic binding:

            ✓ The method declaration is bound to the method definition at runtime.

• Run-time polymorphism is achieved using method overriding.

Example

class Parent {

    void show() {

        System.out.println("Parent class method");

    }

}

class Child extends Parent {

    void show() {

        System.out.println("Child class method");

    }

}

Parent p = new Child();

p.show(); // Output: Child class method

Requirements for Run-Time Polymorphism

To achieve run-time polymorphism, the following conditions must be satisfied:

• Inheritance
• Method Overriding
• Up Casting