To implement Java Program to create your own exception and handle it.

Explanation

This Java program demonstrates the fundamental concept of creating a user-defined exception and subsequently handling that exception when it occurs during program execution.

The core idea is to define a condition (in this case, checking if a person's age is less than 18) that the standard Java exceptions don't naturally cover, and then signal this specific error using our own custom exception class, MyException.

1. Defining the Custom Exception (MyException): A new class named MyException is created that extends Exception. This inheritance is crucial because it marks MyException as a checked exception (meaning the compiler forces you to handle it). The constructor simply calls the parent Exception class's constructor using super(msg) to store the error message provided when the exception is thrown.
2. Main Logic (OwnExceptionEg): In the main method, a variable age is initialized to 15.
3. The Check and Throw: An if statement checks if age < 18. Since $15 < 18$ is true, the program executes the line throw new MyException("Age must be 18 or above");. This immediately halts the normal flow of execution in the try block and searches for a matching catch block.
4. Handling the Exception: The execution jumps to the catch (MyException e) block. This block is specifically designed to catch instances of our custom exception. Inside the catch block, e.printStackTrace() is called. This method prints the complete stack trace of the exception to the console, showing exactly where the error occurred, including the custom message defined during the throw.

Algorithm

1. Define Custom Exception: Create a class named MyException that inherits from java.lang.Exception.
2. Implement Constructor: Define a constructor in MyException that accepts a String message and passes it to the superclass constructor (super(msg)).
3. Main Program Setup: In the main method of OwnExceptionEg, initialize an integer variable (age) to a value that will violate the defined rule (e.g., 15).
4. Implement Try Block: Enclose the potentially error-prone code within a try block.
5. Define Condition: Check if the defined condition (e.g., age < 18) is met.
6. Throw Exception: If the condition is true, use the throw keyword to instantiate and signal the custom exception: throw new MyException("Custom Error Message");.
7. Implement Catch Block: Follow the try block with a catch block specifically targeting the custom exception type (catch (MyException e)).
8. Handle Error: Inside the catch block, use an appropriate method (like e.printStackTrace() or e.getMessage()) to display the error information to the user or log it.