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Comment by ivan_gammel | Hacker News Reader

It is really not a big deal nowadays, the problem of the same scale as having index out of bounds error (no language has good defence against this, yet it is not a catastrophe).

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That's expected (the index out of bound). You have an array, and maybe it grows, you read a number from input, you don't check it against the size of the array because you want to torture the language, use it to get the element at that index and... I'm sure that there is a surprisingly number of different designs of what it should happen and a number of designed ways to ensure that it doesn't happen. But a runtime error is expected.

yes, so are the NPEs - both are runtime errors indicating a bug in the code. NPE was a major source of irritation 20 years ago, but what many people do not know is that debugging NPEs in Java is easier now - they carry more information about the source. And the culture has evolved.

> but what many people do not know is that debugging NPEs in Java is easier now - they carry more information about the source

Unfortunately, no, they don't. Not after your application has been running for a while; newer JVMs arbitrarily decide you don't need the stack trace anymore, and all you see in your logs is "NullPointerException" (unless you still have the logs from several weeks ago, just after the last JVM restart, which might still have the full stack trace). Older JVMs were better, since they always had the full stack trace; debugging NPEs was easier with them.

I think parent was referring to this: https://www.baeldung.com/java-14-nullpointerexception

The problem with array out of bounds is that you'd need to reason about arithmetic expressions over natural numbers. However, in general that's a very thorny problem since one runs squarely into [Gödel's incompleteness theorems](https://en.wikipedia.org/wiki/G%C3%B6del%27s_incompleteness_...). Working around it requires painful restrictions or cause uncertainty over whether the compiler will apply certain optimizations.

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