Example of a Custom Exception in Java

The following code demonstrates an Example of a Custom Exception in Java.

Problem Statement

Create an application that demonstrates how a program throws exceptions if the age of the voter is less than 18.

Solution

// Custom exception class for underage voters
class UnderageVoterException extends Exception {
    public UnderageVoterException(String message) {
        super(message);
    }
}

// Voter class representing a voter's age
class Voter {
    private int age;

    public Voter(int age) {
        this.age = age;
    }

    // Method to check if the voter is eligible
    public void checkEligibility() throws UnderageVoterException {
        if (age < 18) {
            throw new UnderageVoterException("You must be 18 or older to vote.");
        } else {
            System.out.println("You are eligible to vote!");
        }
    }
}

// Main class to demonstrate the program
public class VoterAgeCheck {
    public static void main(String[] args) {
        try {
            // Create a voter with age 16 (underage)
            Voter underageVoter = new Voter(16);
            // Check eligibility, may throw UnderageVoterException
            underageVoter.checkEligibility();
        } catch (UnderageVoterException e) {
            System.out.println("Exception caught: " + e.getMessage());
        }
    }
}

In this program:

We create a custom exception class UnderageVoterException that extends Exception to represent the scenario of an underage voter.
The Voter class contains an age field and a checkEligibility method. If the age of the voter is less than 18, it throws an UnderageVoterException. Otherwise, it prints a message indicating eligibility.
In the main method, we create an instance of the Voter class with an age of 16 (underage), and then we attempt to check their eligibility. Since the age is below 18, the UnderageVoterException is thrown and caught in the catch block, where we print the exception message.

This program demonstrates how to throw and catch a custom exception when the age of a voter is less than 18.

Problem Statement

Solution

Further Reading