Module 2 — Control Flow and Logic

This module teaches how programs make decisions and repeat tasks using conditions and loops. You’ll learn to guide the flow of execution to build interactive, intelligent Java programs.

2.1 — Overview

Every program must make choices: what to do next depends on conditions. Java provides:

• Conditional statements — decide which code to run (if, switch).
• Loops — repeat code while a condition is true (for, while, do-while).
• Control keywords — alter normal flow (break, continue, return).

2.2 — Conditional Statements

if statement

int age = 20;
if (age >= 18) {
    System.out.println("Adult");
}

if-else statement

if (age >= 18) {
    System.out.println("Adult");
} else {
    System.out.println("Minor");
}

if-else if ladder

int score = 85;
if (score >= 90) {
    System.out.println("A");
} else if (score >= 75) {
    System.out.println("B");
} else if (score >= 60) {
    System.out.println("C");
} else {
    System.out.println("Fail");
}

switch statement

Use switch for multiple discrete values.

int day = 3;
switch (day) {
    case 1: System.out.println("Monday"); break;
    case 2: System.out.println("Tuesday"); break;
    case 3: System.out.println("Wednesday"); break;
    default: System.out.println("Other day");
}

2.3 — Loops

Loops allow repetition of code while a condition remains true.

for loop

for (int i = 1; i <= 5; i++) {
    System.out.println("Count: " + i);
}

while loop

int i = 1;
while (i <= 5) {
    System.out.println("Count: " + i);
    i++;
}

do-while loop

The body runs at least once even if the condition is false.

int n = 1;
do {
    System.out.println("Number: " + n);
    n++;
} while (n <= 3);

2.4 — Nested Loops and Flow Control

for (int row = 1; row <= 3; row++) {
    for (int col = 1; col <= 3; col++) {
        System.out.print("* ");
    }
    System.out.println();
}

Control keywords:

• break — exit the nearest loop or switch.
• continue — skip the current iteration and continue the next one.

for (int i = 1; i <= 5; i++) {
    if (i == 3) continue;   // skip 3
    if (i == 5) break;      // stop loop
    System.out.println(i);
}

2.5 — Logical and Relational Operators

Used in conditions to test values.

• Relational: >, <, >=, <=, ==, !=
• Logical: && (AND), || (OR), ! (NOT)

int x = 5, y = 10;
if (x < y && y < 20) {
    System.out.println("Condition true");
}

2.6 — Mini Projects / Practice

2.7 — Summary