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Java Polymorphism
Polymorphism is one of the core principles of Object-Oriented Programming (OOP) in Java. It allows one entity (like a method or object) to take multiple forms. The term polymorphism comes from the Greek words "poly" (many) and "morph" (forms), meaning the ability to process objects differently based on their data type or class.
Types of Polymorphism in Java
Compile-Time Polymorphism (also called Static Polymorphism)
- Achieved through method overloading.
- The method to be called is resolved at compile time.
Example
class Calculator {
// Overloaded methods
int add(int a, int b) {
return a + b;
}
double add(double a, double b) {
return a + b;
}
int add(int a, int b, int c) {
return a + b + c;
}
}
public class Main {
public static void main(String[] args) {
Calculator calc = new Calculator();
System.out.println("Addition of 2 integers: " + calc.add(10, 20)); // Calls the first method
System.out.println("Addition of 2 doubles: " + calc.add(10.5, 20.5)); // Calls the second method
System.out.println("Addition of 3 integers: " + calc.add(10, 20, 30)); // Calls the third method
}
}
Runtime Polymorphism (also called Dynamic Polymorphism)
- Achieved through method overriding.
- The method to be called is determined at runtime based on the actual object
Example
class Animal {
void sound() {
System.out.println("Animals make sounds.");
}
}
class Cat extends Animal {
void sound() {
System.out.println("Cat meows.");
}
}
public class Main {
public static void main(String[] args) {
Animal animal;
animal = new Cat(); // Cat object is assigned to an Animal reference
animal.sound(); // Calls Cat's overridden method
}
}