Should You Use System.exit(num) or Throw a RuntimeException from main() in Java?

Which is a better practice in Java: using System.exit(num) or throwing a RuntimeException from the main() method?

if (errorCondition) {
    throw new RuntimeException("An error occurred");
}

System.exit(1);

When deciding between using `System.exit(num)` and throwing a `RuntimeException` from the `main()` method in Java, it's important to understand the implications of both approaches on application flow and error handling.

public static void main(String[] args) {
    if (errorCondition) {
        throw new RuntimeException("An unrecoverable error occurred.");
    }
    // Some logic 
    if (anotherErrorCondition) {
        System.exit(1);
    }
}

Causes

• Using `System.exit(num)` immediately terminates the JVM, which can lead to abrupt shutdowns of resources and potential loss of data.
• Throwing a `RuntimeException` allows for more controlled error handling and can provide stack traces for debugging.

Solutions

• Use `System.exit(num)` when you need to forcefully terminate the application due to an unrecoverable state, like a critical failure.
• Utilize throwing a `RuntimeException` to allow the program to exit more gracefully, providing details about the error and maintaining resource cleanup.

Mistake: Using `System.exit(num)` in libraries or frameworks, which can lead to unexpected behavior during application lifecycle management.

Solution: Reserve `System.exit(num)` for standalone applications or main methods only.

Mistake: Neglecting proper error handling when throwing a `RuntimeException`, which can obscure issues during debugging.

Solution: Always log the exception message and provide a stack trace for better observability.