Question

I was reading an InfoWorld article (link to Wayback machine since the excerpt was since removed), and came across this little tidbit:

Take the latest version of Java, which
tries to make null-pointer checking
easier by offering shorthand syntax
for the endless pointer testing. Just
adding a question mark to each method
invocation automatically includes a
test for null pointers, replacing a
rat’s nest of if-then statements, such
as:

public String getPostcode(Person person) {
String ans= null;
if (person != null) {
Name nm= person.getName();
if (nm!= null) {
ans= nm.getPostcode();
}
}
return ans
} 

With this:

public String getFirstName(Person person) {
return person?.getName()?.getGivenName();
} 

I’ve scoured the internet (okay, I spent at least 15 minutes googling variations on "java question mark") and got nothing. So, my question: is there any official documentation on this? I found that C# has a similar operator (the "??" operator), but I’d like to get the documentation for the language I’m working in. Or, is this just a use of the ternary operator that I’ve never seen before.

Thanks!

Answer 1

The original idea comes from groovy. It was proposed for Java 7 as part of Project Coin: https://wiki.openjdk.java.net/display/Coin/2009+Proposals+TOC (Elvis and Other Null-Safe Operators), but hasn’t been accepted yet.

The related Elvis operator ?: was proposed to make x ?: y shorthand for x != null ? x : y, especially useful when x is a complex expression.