Control Flow: If-Else and Switch Statements

Control flow statements let a program make decisions and execute different code paths based on conditions — the foundation of all program logic.

If-Else Statement

int marks = 75;

if (marks >= 90) {
    System.out.println("Grade: A");
} else if (marks >= 75) {
    System.out.println("Grade: B");
} else if (marks >= 50) {
    System.out.println("Grade: C");
} else {
    System.out.println("Grade: F");
}

Nested If and Logical Combinations

int age = 20;
boolean hasID = true;

if (age >= 18) {
    if (hasID) {
        System.out.println("Entry allowed");
    } else {
        System.out.println("ID required");
    }
} else {
    System.out.println("Entry denied — underage");
}

The Switch Statement

Switch is a cleaner alternative to long if-else chains when comparing one variable against multiple fixed values.

int day = 3;
String dayName;

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

Why break Matters

Without break, execution "falls through" to the next case automatically — sometimes intentional, but usually a bug.

switch (day) {
    case 1:
    case 2:
    case 3:
    case 4:
    case 5:
        System.out.println("Weekday");
        break;
    case 6:
    case 7:
        System.out.println("Weekend");
        break;
}

The Ternary Operator

A compact shorthand for simple if-else assignments:

int a = 10, b = 20;
int max = (a > b) ? a : b;   // max = 20

Interview tip: Since Java 14, switch can also be written as an expression with arrow syntax (case 3 -> "Wednesday";), removing the need for break entirely — worth mentioning if asked about modern Java features.