Question Mark "?" in apex code

Question

I was working on a controller, and came across a question mark in the code. What is this used for? I've searched for it but haven't found what it is used for.

if(dfield.isPermissionable()){
    string fieldAPIName = dfield.getName().endsWith('Id') && !dfield.isCustom() ? dfield.getName().removeEnd('Id') : dfield.getName();
    fieldList.add(fieldAPIName);
    fieldAPIToLabelMap.put(fieldAPIName,dfield.getLabel());
    selectedFields.add(fieldAPIName);
    tempList.add(dfield.getLabel() + ':' + fieldAPIName);
}

Answer 1

It is called as ternary operator

x ? y : z

Ternary operator (Right associative). This operator acts as a short-hand for if-then-else statements. If x, a Boolean, is true, y is the result. Otherwise z is the result. Note that x cannot be null.

dfield.isCustom() ? dfield.getName().removeEnd('Id') : dfield.getName();

The above statement means that is if dfield.isCustom() is true dfield.getName().removeEnd('Id') value will be returned else dfield.getName() value will be returned.

Answer 2

Since Winter '21, the question mark is also used in Apex as a null-safe operator:

String myVal = a?.b // Evaluates to: a == null? Null : a.b

You may review the release notes (https://releasenotes.docs.salesforce.com/en-us/winter21/release-notes/rn_apex_SafeNavigationOperator.htm)