https://www.codebyamir.com/blog/stop-returning-null-in-java

“I call it my billion-dollar mistake.

At that time, I was designing the first comprehensive type system for references in an object-oriented language.

My goal was to ensure that all use of references should be absolutely safe, with checking performed automatically by the compiler. But 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.”