Nesting and the dangling else

Conditions nest: an if inside an if.

if (age >= 13) {
    if (hasPermission) {
        System.out.println("admit");
    } else {
        System.out.println("permission needed");
    }
}

Nesting is equivalent to && when there is no else on the inner test: if (a) { if (b) { X } } runs X exactly when both hold. Prefer flat && when you can — but read nested code fluently, the exam presents it constantly.

Dangling else — an else binds to the nearest unmatched if, not the one indentation suggests:

if (a < 5)
    if (a > 2)
        System.out.println("3-4");
else
    System.out.println("else");   // belongs to inner if!

With a = 10: outer true → enter; inner 10 > 2 false → else fires, prints "else". With a = 0: outer false → nothing prints at all. Brace your intentions and trace honestly.

Common logical errors: flipped comparisons (< for <=), overlapping ranges, testing x == 5 || 6 (always true — 6 is truthy-wrong here: it must be x == 5 || x == 6), and inverted guards.