Multiple-Choice Strategy

Control Flow: Conditionals and Loops

By the end of this lesson, you will be able to write if, else if, and else statements, use while and for loops, and trace through code to determine its output.

Boolean Expressions

Relational operators:

Operator	Meaning
==	equal to
!=	not equal to
<	less than
>	greater than
<=	less than or equal to
>=	greater than or equal to

Logical operators:

Operator	Meaning	Example
&&	AND (both must be true)	x > 0 && x < 10
||	OR (at least one must be true)	x < 0 || x > 100
!	NOT (negation)	!done

Short-circuit evaluation:

• &&: if the left side is false, the right side is NOT evaluated
• ||: if the left side is true, the right side is NOT evaluated

if / else if / else

if (condition1) {
    // executes if condition1 is true
} else if (condition2) {
    // executes if condition1 is false AND condition2 is true
} else {
    // executes if all conditions above are false
}

Example:

int score = 78;
String grade;

if (score >= 90) {
    grade = "A";
} else if (score >= 80) {
    grade = "B";
} else if (score >= 70) {
    grade = "C";
} else if (score >= 60) {
    grade = "D";
} else {
    grade = "F";
}
// grade is "C"

Key point: once a condition is true and its block executes, the remaining else if and else blocks are skipped.