Programmers use Null as different flags. It can hint an absence, an undefined value, en error etc.
Multiple semantics lead to coupling and errors.
Coupling among the callers and the senders.
Mismatch among the callers and the senders.
Null is not polymorphic with real objects. Hence Null Pointer Exception.
Null does not exist on real world. Thus it violates Bijection Principle.
- Apis, Databases and external systems where NULL does exist.
Most Linters can show null usages and warn us.
- Null is the billion dollar mistake. Yet, most program languages support them and libraries suggest its usage.
I couldn't resist the temptation to put in a null reference, simply because it was so easy to implement. This has led to innumerable errors, vulnerabilities, and system crashes, which have probably caused a billion dollars of pain and damage in the last forty years.