I’ve already shown in another post how we can utilize the Optional type of Java 8 to prevent null checks. This post describes a couple of techniques how to prevent writing needless null checks by utilizing new features of Java 8 like lambda expressions. But luckily things get better in Java Version 8. Unfortunately Java doesn’t provide such a syntactic sugar. Since null checks are kinda cumbersome and painful many languages add special syntax for handling null checks via null coalescing operators - also known as elvis operator in languages like Groovy or Kotlin.

So what can we do to prevent NullPointerExceptions at all? Well, the obvious answer is to add null checks all around the place. 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.Īnyways, we have to deal with it.

But I couldn’t resist the temptation to put in a null reference, simply because it was so easy to implement. My goal was to ensure that all use of references should be absolutely safe, with checking performed automatically by the compiler. At that time, I was designing the first comprehensive type system for references in an object oriented language (ALGOL W). It was the invention of the null reference in 1965. Tony Hoare, the inventor of the null reference apologized in 2009 and denotes this kind of errors as his billion-dollar mistake.

It’s by far the most prevalent kind of error in Java and many other programming languages as well. But also intermediate and expert programmers get around this error every now and then. How to prevent the famous NullPointerException in Java? This is one of the key questions every Java beginner will ask sooner or later.

Kotlin map not null