The use of a ? denotes a ternary operator. Ternary operators are java's shorthand for if-else statements. You find them often used when you need to do a quick check before assigning one of two values to a variable, or for any other occasion where you'd have a simple bodied if-else statement returning or assigning something based on a condition. It's probably best compared like-so:
int value1 = 5;
int value2 = 10;
int biggestValue;
if(value1 > value2) {
biggestValue = value1;
} else {
biggestValue = value2;
}
Whilst the previous code snippet works perfectly fine, some people might find it easier or cleaner to rewrite the statement as a ternary. The same code above could be rewritten as a ternary:
int value1 = 5;
int value2 = 10;
int biggestValue = value1 > value2 ? value1 : value2;
This alternative takes the exact same steps as before: It evaluates whether value1 is greater than value2, assigning biggestValue the greatest of the two values. As you can see, the basic structure of a ternary operator is as follows:
someVariable = condition ? expressionIfTrue : expressionIfFalse;
just to clarify, ternary operations always return a value, so you are expected to do something with said value. It's not possible to, for instance, put two void method calls as your expressions. Beyond that caveat, they're a nifty holdover from C that can be useful in a pinch. The only thing is to of course ensure that you do not negatively impact your code's readability using it. Whilst shorter code is often nice, hiding complex operations in a single line can very easily sidetrack anyone trying to follow your work.
