if, else, and else-if chains

if runs a block only when its boolean is true; else is the other road.

if (score >= 60) {
    System.out.println("pass");
} else {
    System.out.println("fail");
}

else-if chains test in order and stop at the first true branch:

if (score >= 90) {
    grade = 'A';
} else if (score >= 80) {
    grade = 'B';
} else if (score >= 70) {
    grade = 'C';
} else {
    grade = 'F';
}

Order is everything: with score = 95, the first branch fires and the rest are skipped. If you tested score >= 70 first, every score 70+ would get 'C' — a classic ordering bug.

Boundaries. >= vs > decides who owns the edge. Decide deliberately: does 90 earn an A? Then score >= 90, not > 90. When the chain ends with else, one branch always runs; without it, maybe none do.

Braces are optional for a single statement — but the AP exam loves to ask what happens when a brace-less if meets a dangling else. Trace the indentation is a lie case:

if (x > 10)
    System.out.println("big");
    System.out.println("done");   // NOT inside the if — always runs!