Java – Polymorphism

Polymorphism:

• Polymorphism is the concept where object behaves differently in different situations.
• Defining an Object(class) that shows different functionality with same name.

Polymorphism is of two types:

1. Compile time polymorphism
2. Runtime polymorphism

Compile time polymorphism:

• It is method overloading technique.
• Defining multiple methods with same name and different signature(parameters).
• Parameters can be either different length or different type.
• Overloading belongs to single class(object).

class Calculator {             void add(int x, int y) {                         int sum = x+y;                         System.out.println(“Sum of 2 numbers is : ” + sum);             }             void add(int x, int y, int z) {                         int sum = x+y+z;                         System.out.println(“Sum of 3 numbers is : ” + sum);             } } class Main {             public static void main(String[] args) {                         Calculator calc = new Calculator();                         calc.add(10, 20);                         calc.add(10, 20, 30);             } }

println() method is pre-defined and overloaded. Hence it can print any type of data:

class Overload {             public static void main(String[] args) {                         System.out.println(10);                         System.out.println(12.345);                         System.out.println(‘g’);                         System.out.println(“java”);             } }

Can we overload Constructor?

• Yes allowed.
• Overloaded constructors can connect using this() method is called Constructor chaining.

Can we overload main() method ?

• Yes.
• JVM invokes only standard main() method.
• Other main() methods must be called manually like other methods in application.

class Pro {             public static void main(String[] args) {                         System.out.println(“Standard main invoked by JVM”);                         Pro obj = new Pro();                         obj.main();                         Pro.main(10);             }             void main(){                         System.out.println(“No args main”);             }             static void main(int x){                         System.out.println(“One arg main”);             } }

Can we write main() as ‘static public’ instead of ‘public static’?

• We can specify modifiers and access modifiers in any order. All the following declarations are valid in java.

public static final int a;	static public final int a;	final static public int a;
final public static int a;	static final public int a;	public final static int a;