The ternary operator

Key points

• condition ? whenTrue : whenFalse is an expression, so it produces a value you can assign or return.
• Only the branch that is needed runs, exactly like &&. The other side is never evaluated.
• Both branches must have compatible types; the result type is worked out at compile time.
• Chain it for a small ladder, but stop at two or three levels. Beyond that use if or a switch expression.
• An int branch beside a null branch boxes to Integer; unboxing that into an int throws.
• Perfect for defaults and singular/plural text. Poor for anything with a side effect.

Example

public class Main {

    static String grade(int score) {
        return score >= 90 ? "A"
             : score >= 75 ? "B"
             : score >= 60 ? "C"
             : "F";
    }

    public static void main(String[] args) {
        for (int s : new int[]{95, 80, 61, 42}) {
            System.out.println(s + " -> " + grade(s));
        }

        String name = null;
        System.out.println("null-safe label: " + (name != null ? name : "anonymous"));

        int a = 7, b = 12;
        System.out.println("max without Math.max: " + (a > b ? a : b));

        int count = 1;
        System.out.println(count + (count == 1 ? " file" : " files") + " copied");

        Integer boxed = args.length > 0 ? args.length : null;
        System.out.println("mixing int and null boxes to Integer: " + boxed);
        System.out.println("assigning that to an int would throw NullPointerException");
    }
}

Use a ternary when you need a value, an if when you need a statement.