Notes on "Clean Code - Error Handling" chapter

• “Error handling is important, but if it obscures logic, it’s wrong”
• Using exceptions make it possible to decouple business logic from error handling.
• Using unchecked exceptions in Java is preferable. Checked exceptions violate Open/Closed principle. Example:

class A {
    void methodA() {}
}

class B {
    void methodB() {
        new A().methodA();
    }
}

class C {
    public static void main(String[] args]) {
        new B().methodB();
    }
}

If I want to add checked exception to methodA() I need to change signature iun methodB() - which shouldn’t care about it at all. Encapsulation is broken!

• Provide context to exception which explains why the operation failed.
• Sometimes it is required to handle couple different exception types coming from a single method call in the same way. In such case, it might be better to create a wrapper class, which will encapsulate that call and throw a single, common exception type (containing the original cause). This way the original invocation will need to handle only a single exception - this will reduce duplication.
• Don’t return null values - return empty/guard values (Special Case Pattern).
• Don’t pass null values as arguments.