Discuss polymorphism using real-life example.

Inheritance in Java is a mechanism in which one object acquires all the properties and behaviors of the parent object. Using inheritance, we can create a general class that defines traits common to a set of related items. This class can then be inherited by other, more specific classes, each adding those things that are unique to it.

Java strongly supports the concept of reusability. The Java classes can be reused in several ways. Once a class has been written and tested, it can be adapted by another programmer to suit their requirements. This is basically done by creating new classes, reusing the properties of the existing ones. The logic behind inheritance in Java is that we can create new classes that from existing classes. When you inherit from an existing class, you can reuse methods and fields of the parent class, and you can add new methods and fields also. That

To inherit a class we use extends keyword. Here class XYZ is child class and class ABC is parent class. The class XYZ is inheriting the properties and methods of ABC class.

class XYZ extends ABC
{
...
...

}

Try and catch are keywords that represent the handling of exceptions due to data or coding errors during program execution. A try block is the block of code in which exceptions occur. A catch block catches and handles try block exceptions.

Syntax of try catch in java

try
{     //statements that may cause an exception
}
Catch (exception (type) e (object))?
{      //error handling code
}

Syntax of try catch in java

try
{     //statements that may cause an exception
}
Catch (exception (type) e (object))?
{      //error handling code
}

In computer programming languages, the term default constructor can refer to a constructor that is automatically generated by the compiler in the absence of any programmer-defined constructors and is usually a nullary constructor.

There are two rules defined for the constructor.

1. Constructor name must be the same as its class name
2. A Constructor must have no explicit return type
3. A Java constructor cannot be abstract, static, final, and synchronized

Every time an object is created using new() keyword, at least one constructor is called. It calls a default constructor.

Note: It is called constructor because it constructs the values at the time of object creation. It is not necessary to write a constructor for a class. It is because java compiler creates a default constructor if your class does not have any.

There are two types of constructors in Java:

1. Default constructor (no-arg constructor): A constructor is called Default Constructor when it does not have any parameter.
2. Parameterized constructor: A constructor which has a specific number of parameters is called a parameterized constructor.

The default constructor is used to provide the default values to the object like 0, null, etc., depending on the type.

Example of default constructor that displays the default values

//Let us see another example of default constructor  
//which displays the default values  
class Student3{  
int id;  
String name;  
//method to display the value of id and name  
void display(){System.out.println(id+" "+name);}  
  
public static void main(String args[]){  
//creating objects  
Student3 s1=new Student3();  
Student3 s2=new Student3();  
//displaying values of the object  
s1.display();  
s2.display();  
}  
}  

0 null
0 null

The parameterized constructor is used to provide different values to the distinct objects. However, you can provide the same values also.

Example of parameterized constructor

In this example, we have created the constructor of Student class that have two parameters. We can have any number of parameters in the constructor.

//Java Program to demonstrate the use of parameterized constructor  
class Student4{  
    int id;  
    String name;  
    //creating a parameterized constructor  
    Student4(int i,String n){  
    id = i;  
    name = n;  
    }  
    //method to display the values  
    void display(){System.out.println(id+" "+name);}  
   
    public static void main(String args[]){  
    //creating objects and passing values  
    Student4 s1 = new Student4(111,"Karan");  
    Student4 s2 = new Student4(222,"Aryan");  
    //calling method to display the values of object  
    s1.display();  
    s2.display();  
   }  
}  

111 Karan
222 Aryan