Java OO Tutorial - Polymorphism

Polymorphism is a fundamental concept in Java that refers to the ability of objects to take on multiple forms.  

class Primary {
	public void sameName() {
		System.out.println("I am from Primary Class");
	}
}

class SecondaryA extends Primary {
	public void sameName() {
		System.out.println("I am from SecondaryA Class");
	}	
}

class SecondaryB extends Primary {
	public void sameName() {
		System.out.println("I am from SecondaryB Class");
	}	
}

public class Main {	
	
	public static void main(String[] args) {
		
		Primary primObj = new Primary();
		Primary secAObj = new SecondaryA();
		Primary secBObj = new SecondaryB();		
		
		primObj.sameName();
		secAObj.sameName();
		secBObj.sameName();		
	}		
}

Here's an explanation of the code block by block: 

class Primary {
	public void sameName() {
		System.out.println("I am from Primary Class");
	}
}

This code defines a class Primary with a method sameName(), which simply prints "I am from Primary Class" to the console. 

class SecondaryA extends Primary {
	public void sameName() {
		System.out.println("I am from SecondaryA Class");
	}	
}

This code defines a subclass SecondaryA of the Primary class. SecondaryA also has a sameName() method, but in this case, it prints "I am from SecondaryA Class" to the console. Since SecondaryA extends Primary, it inherits the sameName() method from Primary but overrides it with its own implementation. 

class SecondaryB extends Primary {
	public void sameName() {
		System.out.println("I am from SecondaryB Class");
	}	
}

This code defines another subclass SecondaryB of the Primary class. SecondaryB also has a sameName() method, which prints "I am from SecondaryB Class" to the console. Again, since SecondaryB extends Primary, it inherits the sameName() method from Primary but overrides it with its own implementation. 

public class Main {	
	
	public static void main(String[] args) {
		
		Primary primObj = new Primary();
		Primary secAObj = new SecondaryA();
		Primary secBObj = new SecondaryB();		
		
		primObj.sameName();
		secAObj.sameName();
		secBObj.sameName();		
	}		
}

This code defines the Main class with a main() method. In the main() method, we create objects of Primary, SecondaryA, and SecondaryB classes and assign them to variables of type Primary. We then call the sameName() method on each of these objects. The output will be: 

I am from Primary Class
I am from SecondaryA Class
I am from SecondaryB Class

This demonstrates the concept of polymorphism in Java, where the same method (sameName()) can be called on different objects (primObj, secAObj, and secBObj), and the implementation of the method that is called depends on the actual type of the object that the method is called on.