Throwing exceptions and custom exceptions explain with example in Java.

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Ravi Vishwakarma · Answer

1. Throwing Exceptions in Java
In Java, you can throw exceptions using the throw keyword.
Syntax:
throw new ExceptionType("Error Message");
Example:
public class ThrowExample {
    public static void checkPersonAge(int age) {
        if (age andlt; 16) {
            throw new IllegalArgumentException("Age must be 16 or above of a person");
        } else {
            System.out.println("Access granted");
        }
    }
    public static void main(String[] args) {
        checkPersonAge(16);  // This will throw an exception
    }
}
2. Custom Exceptions in Java
You can create your own exceptions by extending Exception (checked) or
RuntimeException (unchecked).
Example of Custom Exception:
// Step 1: Create a custom exception
class InvalidAgeException extends Exception {
    public InvalidAgeException(String message) {
        super(message);
    }
}
// Step 2: Use the custom exception
public class CustomExceptionExample {
    public static void validatePersonAge(int age) throws InvalidAgeException {
        if (age andlt; 16) {
            throw new InvalidAgeException("You must be at least 16 years old for person.");
        }
        System.out.println("Age is valid");
    }
    public static void main(String[] args) {
        try {
            validatePersonAge(15);  // This will throw InvalidAgeException
        } catch (InvalidAgeException e) {
            System.out.println("Caught Exception: " + e.getMessage());
        }
    }
}
Summary:
Feature
Explanation
throw
Used to explicitly throw an exception
throws
Declares that a method can throw exceptions
Custom Exception
User-defined exception for specific errors
extends Exception
For checked exceptions
extends RuntimeException
For unchecked exceptions
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Throwing exceptions and custom exceptions explain with example in Java.

Ravi Vishwakarma

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1 Answers

1. Throwing Exceptions in Java

2. Custom Exceptions in Java

Summary:

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Feature	Explanation
`throw`	Used to explicitly throw an exception
`throws`	Declares that a method can throw exceptions
Custom Exception	User-defined exception for specific errors
`extends Exception`	For checked exceptions
`extends RuntimeException`	For unchecked exceptions