How to create a custom exception in Java

Why we need custom Exception ?
How to create a custom exception ?
Write code to create a Custom Exception

All these are questions usually asked in a Java interview .So my today's post on how to create a custom exception in java .

As we know There are two types of Exception :
1. Checked Exception
2. Unchecked Exception

Both these exceptions have a common parent class Exception .So ,in same order if we have to create a custom exception ,we need to extend Exception class.

Ok , let me explain the process step by step .

1. Any custom exception should extend Exception Class .

2. There should be a proper name given to the Exception ,For example if there is an exception related to Invalid age name can be given as InvalidAgeException

public class InvalidAgeException extends Exception {}

public class InvalidAgeException extends Exception {
private int age;

public InvalidAgeException ()
public InvalidAgeException (String message, int age)


   this.age = age;


In the above way we can define two constructors of InvalidAgeException with message and without message

Usage of custom Exception:

Below is the program with usage of custom exception.

public class CustomExceptionDemo 

private static final Map<Integer, String> employee = new HashMap<>(); 




   employee.put(103"Troy"); }

 public static void main(String args[])

     CustomExceptionDemo t = new CustomExceptionDemo();

    t.getAge(1000); } 

public String getAge(int age)


     if (employee.get(age) == null)

   throw new InvalidAgeException ("No such employee exists", age);

return employee.get(name);



Post a Comment