07_Chapter_7_Error_Handling.md

Chapter 7: Error Handling [Slide]

Error handling is important, but if it obscures logic, it’s wrong.

Use Exceptions Rather Than Return Codes

Using exception for error handling helps separate business logic from error code

Write Your Try-Catch-Finally Statement First

Your catch has to leave your program in a consistent state, no matter what happens in the try.

So writing try-catch statement first ensures your code is not jeopardizing consistency, and it will make structure of code simpler.

Use Unchecked Exceptions

Checked exceptions force any change in low level code to affect higher levels.

This will clearly violate Open/Closed principle.

Provide Context with Exceptions

write a good and self-explanatory message with enough context to be shown in exception stack trace console

Define Exception Classes in Terms of a Caller’s Needs

• Use wrapper class to compound different exceptions thrown from a function into a common exception type we care about
• Use different classes only if there are times when you want to catch one exception and allow the other one to pass through.

Define the Normal Flow

Encapsulate special cases inside your code so that the caller don't have to deal with default values when there is an exception

Don’t Return Null

Instead of returning null you can return a special object like Failure or if you're returning a list of object you can simple return an empty list if you really need to return null, mention it in your function name like: getFirstOrNull()

Don’t Pass Null

• avoid passing null when your argument does not support null
• If you really want to pass null at least use a nullable type or annotation or any other proper means to declare your parameter as nullable