Unit 4: Conditional Statements

Opening Hook — The Code Behind Every IRCTC Ticket

Learning Outcomes — Bloom's Taxonomy Mapped (12 Outcomes)

Concept Explanation — Conditional Statements from Scratch

1. The if Statement — Your First Decision Maker

The if statement is the simplest form of decision-making in Java. It tests a boolean condition and executes a block of code only if the condition is true.

Java
if (condition) {
    // code executes ONLY when condition is true
}

Java
// Example: Check if a student passed
int marks = 72;

if (marks >= 40) {
    System.out.println("Congratulations! You passed the exam.");
}

if (marks >= 90) {
    System.out.println("Outstanding! You're a topper.");
}

2. if-else and Nested if-else — Two-Way and Multi-Way Decisions

The if-else Statement

When you need two paths — one for true, one for false — use if-else.

Java
int age = 16;

if (age >= 18) {
    System.out.println("Eligible to vote in Indian elections.");
} else {
    System.out.println("Not eligible to vote yet. Wait " + (18 - age) + " more years.");
}

The else-if Ladder (Chained if-else)

When you have multiple conditions to check sequentially, use the else-if ladder. Java evaluates from top to bottom and executes the first matching block.

🏆 Full Program: GradeCalculator

Java
import java.util.Scanner;

public class GradeCalculator {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        System.out.print("Enter your marks (0-100): ");
        int marks = sc.nextInt();

        char grade;
        String remark;

        if (marks < 0 || marks > 100) {
            System.out.println("Invalid marks! Must be 0-100.");
            return;
        } else if (marks >= 90) {
            grade = 'O';   // Outstanding
            remark = "Outstanding! Top of the class.";
        } else if (marks >= 80) {
            grade = 'A';
            remark = "Excellent performance!";
        } else if (marks >= 70) {
            grade = 'B';
            remark = "Good job, keep improving.";
        } else if (marks >= 60) {
            grade = 'C';
            remark = "Average. You can do better.";
        } else if (marks >= 40) {
            grade = 'D';
            remark = "Below average. Needs improvement.";
        } else {
            grade = 'F';
            remark = "Fail. Please re-appear.";
        }

        System.out.println("Grade: " + grade);
        System.out.println("Remark: " + remark);
    }
}

Nested if-else — Decision Inside a Decision

Sometimes you need to make a second decision within the first. This is nesting — an if inside another if.

Java
// Nested if-else: Check eligibility for Indian Army
int age = 20;
double heightCm = 170.5;
boolean isCitizen = true;

if (isCitizen) {
    if (age >= 17 && age <= 21) {
        if (heightCm >= 157.5) {
            System.out.println("✅ Eligible for Indian Army recruitment.");
        } else {
            System.out.println("❌ Height requirement not met (min 157.5 cm).");
        }
    } else {
        System.out.println("❌ Age must be between 17–21 years.");
    }
} else {
    System.out.println("❌ Must be an Indian citizen.");
}

3. Traditional switch-case — The Multi-Way Branch

Analogy: Think of switch-case like an IRCTC ticket counter. You walk up and say your class — 1A, 2A, 3A, SL, or General. The counter clerk doesn't ask you 5 questions sequentially ("Is it 1A? No? Is it 2A? No?"). Instead, they hear your class once and jump straight to the right fare formula. That's exactly how switch works — it evaluates the expression once and jumps to the matching case.

Java
switch (expression) {
    case value1:
        // code for value1
        break;
    case value2:
        // code for value2
        break;
    // ... more cases
    default:
        // code if no case matches
}

🏆 Full Program: SimpleATM (switch)

Java
import java.util.Scanner;

public class SimpleATM {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        double balance = 25000.00; // Initial balance in ₹

        System.out.println("╔══════════════════════════╗");
        System.out.println("║    SBI ATM — Main Menu   ║");
        System.out.println("╠══════════════════════════╣");
        System.out.println("║  1. Check Balance        ║");
        System.out.println("║  2. Withdraw Cash        ║");
        System.out.println("║  3. Deposit Cash         ║");
        System.out.println("║  4. Mini Statement       ║");
        System.out.println("║  5. Exit                 ║");
        System.out.println("╚══════════════════════════╝");
        System.out.print("Enter your choice (1-5): ");

        int choice = sc.nextInt();

        switch (choice) {
            case 1:
                System.out.println("💰 Your balance: ₹" + balance);
                break;

            case 2:
                System.out.print("Enter amount to withdraw: ₹");
                double withdraw = sc.nextDouble();
                if (withdraw > balance) {
                    System.out.println("❌ Insufficient balance!");
                } else if (withdraw % 100 != 0) {
                    System.out.println("❌ Amount must be multiple of ₹100");
                } else {
                    balance -= withdraw;
                    System.out.println("✅ ₹" + withdraw + " withdrawn. New balance: ₹" + balance);
                }
                break;

            case 3:
                System.out.print("Enter amount to deposit: ₹");
                double deposit = sc.nextDouble();
                balance += deposit;
                System.out.println("✅ ₹" + deposit + " deposited. New balance: ₹" + balance);
                break;

            case 4:
                System.out.println("📄 Mini Statement:");
                System.out.println("   Current Balance: ₹" + balance);
                System.out.println("   Account Type: Savings");
                System.out.println("   Branch: SBI Main Branch");
                break;

            case 5:
                System.out.println("🙏 Thank you for banking with SBI. Namaste!");
                break;

            default:
                System.out.println("❌ Invalid choice! Please select 1-5.");
        }
    }
}

⚠️ The Fall-Through Trap

If you forget break, Java doesn't stop at the matching case — it "falls through" and executes ALL subsequent cases until it hits a break or the end of the switch block.

Java
// DANGEROUS: Missing break statements!
int day = 3;
switch (day) {
    case 1: System.out.println("Monday");
    case 2: System.out.println("Tuesday");
    case 3: System.out.println("Wednesday");  // ← matches here
    case 4: System.out.println("Thursday");   // ← falls through!
    case 5: System.out.println("Friday");     // ← falls through!
    default: System.out.println("Weekend");   // ← falls through!
}

🏆 Full Program: DayOfWeekPrinter

Java
import java.util.Scanner;

public class DayOfWeekPrinter {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        System.out.print("Enter day number (1-7): ");
        int day = sc.nextInt();

        String dayName;
        String type;

        switch (day) {
            case 1: dayName = "Monday";    type = "Weekday"; break;
            case 2: dayName = "Tuesday";   type = "Weekday"; break;
            case 3: dayName = "Wednesday"; type = "Weekday"; break;
            case 4: dayName = "Thursday";  type = "Weekday"; break;
            case 5: dayName = "Friday";    type = "Weekday"; break;
            case 6: dayName = "Saturday";  type = "Weekend"; break;
            case 7: dayName = "Sunday";    type = "Weekend"; break;
            default:
                System.out.println("Invalid day number!");
                return;
        }

        System.out.println("Day: " + dayName + " (" + type + ")");
    }
}

4. Enhanced Switch (Java 14+) — Arrow Syntax & Switch Expressions

Java 14 introduced the enhanced switch with arrow syntax (->). This eliminates the need for break and prevents fall-through bugs entirely.

Arrow Syntax (No Fall-Through)

Java (14+)
int day = 3;

switch (day) {
    case 1 -> System.out.println("Monday");
    case 2 -> System.out.println("Tuesday");
    case 3 -> System.out.println("Wednesday");
    case 4 -> System.out.println("Thursday");
    case 5 -> System.out.println("Friday");
    case 6, 7 -> System.out.println("Weekend! 🎉");
    default -> System.out.println("Invalid day");
}

Key differences from traditional switch:

Switch Expression with yield (Java 14+)

A switch expression returns a value. For multi-line blocks, use the yield keyword to specify what to return.

Java (14+)
int monthNum = 8;

String season = switch (monthNum) {
    case 12, 1, 2 -> "Winter ❄️";
    case 3, 4, 5 -> "Spring 🌸";
    case 6, 7, 8, 9 -> "Monsoon 🌧️";
    case 10, 11 -> "Autumn 🍂";
    default -> "Invalid month";
};  // Note: semicolon at end — it's an expression!

System.out.println("Season: " + season);

Java (14+) — yield in multi-line blocks
String travelClass = "2A";

double fare = switch (travelClass) {
    case "1A" -> {
        System.out.println("First AC — Premium luxury");
        yield 4825.0;
    }
    case "2A" -> {
        System.out.println("Second AC — Comfortable");
        yield 2770.0;
    }
    case "3A" -> {
        System.out.println("Third AC — Budget AC");
        yield 1950.0;
    }
    case "SL" -> {
        System.out.println("Sleeper — Most popular");
        yield 680.0;
    }
    case "GEN" -> {
        System.out.println("General — Unreserved");
        yield 350.0;
    }
    default -> {
        System.out.println("Unknown class");
        yield 0.0;
    }
};

System.out.println("Fare: ₹" + fare);

🏆 Full Program: IndianRailwayFareCalculator

Java
import java.util.Scanner;

public class IndianRailwayFareCalculator {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);

        System.out.println("╔═══════════════════════════════════════╗");
        System.out.println("║   🚂 IRCTC Fare Calculator v2.0      ║");
        System.out.println("╚═══════════════════════════════════════╝");

        System.out.print("Enter base distance fare (₹): ");
        double baseFare = sc.nextDouble();
        sc.nextLine(); // consume newline

        System.out.println("Travel Classes: 1A | 2A | 3A | SL | GEN");
        System.out.print("Enter your class: ");
        String travelClass = sc.nextLine().toUpperCase().trim();

        System.out.print("Tatkal booking? (yes/no): ");
        String tatkal = sc.nextLine().toLowerCase().trim();

        System.out.print("Senior citizen? (yes/no): ");
        String senior = sc.nextLine().toLowerCase().trim();

        double multiplier;
        String className;

        // Switch on travel class to set multiplier
        switch (travelClass) {
            case "1A":
                multiplier = 6.0;
                className = "First AC";
                break;
            case "2A":
                multiplier = 3.5;
                className = "Second AC";
                break;
            case "3A":
                multiplier = 2.5;
                className = "Third AC";
                break;
            case "SL":
                multiplier = 1.0;
                className = "Sleeper";
                break;
            case "GEN":
                multiplier = 0.5;
                className = "General";
                break;
            default:
                System.out.println("❌ Invalid travel class!");
                return;
        }

        double totalFare = baseFare * multiplier;

        // Apply Tatkal surcharge using if-else
        if (tatkal.equals("yes")) {
            if (travelClass.equals("1A") || travelClass.equals("2A")) {
                totalFare += 400; // AC Tatkal charge
            } else if (travelClass.equals("3A")) {
                totalFare += 300;
            } else if (travelClass.equals("SL")) {
                totalFare += 200;
            }
            // GEN has no Tatkal
        }

        // Apply senior citizen discount using if
        if (senior.equals("yes")) {
            totalFare *= 0.6; // 40% discount
            System.out.println("🧓 Senior citizen discount (40%) applied!");
        }

        System.out.println("\n════════════════════════════════");
        System.out.println("🎫 BOOKING SUMMARY");
        System.out.println("   Class     : " + className);
        System.out.println("   Base Fare : ₹" + baseFare);
        System.out.println("   Multiplier: " + multiplier + "x");
        System.out.println("   Tatkal    : " + (tatkal.equals("yes") ? "Yes" : "No"));
        System.out.println("   Senior    : " + (senior.equals("yes") ? "Yes" : "No"));
        System.out.printf("   TOTAL FARE: ₹%.2f%n", totalFare);
        System.out.println("════════════════════════════════");
    }
}

5. Conditional Logic Design Patterns

Nested if-else vs Chained if-else — When to Use What?

if-else vs switch-case — Decision Guide

Learn by Doing — 3-Tier Lab: IRCTC Fare Calculator

Java
import java.util.Scanner;

public class BasicFareCalculator {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);

        System.out.print("Enter distance (km): ");
        int distance = sc.nextInt();
        sc.nextLine();

        System.out.print("Enter class (1A/2A/3A/SL/GEN): ");
        String cls = sc.nextLine().toUpperCase();

        double ratePerKm;

        if (cls.equals("1A")) {
            ratePerKm = 4.25;
        } else if (cls.equals("2A")) {
            ratePerKm = 2.50;
        } else if (cls.equals("3A")) {
            ratePerKm = 1.75;
        } else if (cls.equals("SL")) {
            ratePerKm = 0.80;
        } else if (cls.equals("GEN")) {
            ratePerKm = 0.35;
        } else {
            System.out.println("Invalid class!");
            return;
        }

        double fare = distance * ratePerKm;
        System.out.printf("Fare for %d km in %s: ₹%.2f%n", distance, cls, fare);
    }
}

Terminal
javac BasicFareCalculator.java
java BasicFareCalculator

Problem Set — Practice Questions

🔤 Syntax Questions (5)

S1. Write the syntax of a traditional switch-case statement with break and default.

S2. Write the syntax of an enhanced switch expression (Java 14+) with arrow syntax that returns a value.

S3. Write a nested if-else structure that checks three conditions: citizenship, age range, and qualification.

S4. What is the difference between yield and return in a switch expression? Write a code snippet demonstrating yield.

S5. Write a switch-case that groups multiple case labels together (e.g., Monday–Friday as "Weekday") using (a) traditional fall-through and (b) enhanced comma-separated syntax.

💻 Programming Questions (8)

P1. Write a Java program that takes a month number (1-12) and prints the number of days in that month (handle leap year for February using nested if).

P2. Create an IncomeTaxCalculator that takes annual income and calculates tax using the Indian tax slabs: 0-2.5L → 0%, 2.5-5L → 5%, 5-10L → 20%, 10L+ → 30%.

P3. Build a VowelConsonantChecker using switch-case that takes a character and prints whether it's a vowel, consonant, digit, or special character.

P4. Write a BMICalculator that takes weight (kg) and height (m), calculates BMI, and classifies it as Underweight/Normal/Overweight/Obese using if-else.

P5. Create a SimpleCalculator that takes two numbers and an operator (+, -, *, /, %) using switch-case and performs the calculation with division-by-zero handling.

P6. Write an ElectricityBillCalculator using Indian tariff slabs: 0-100 units → ₹1.5/unit, 101-300 → ₹3.5/unit, 301-500 → ₹5.5/unit, 500+ → ₹8/unit. Use if-else chain.

P7. Build a TrafficLightSimulator using enhanced switch (Java 14+) that takes a color ("RED", "YELLOW", "GREEN") and prints the action with duration in seconds.

P8. Create an AgeGroupClassifier that takes age and classifies into: Infant (0-1), Toddler (2-4), Child (5-12), Teenager (13-19), Adult (20-59), Senior (60+). Handle negative ages as invalid.

🏭 Industry-Level Questions (3)

I1. Paytm Cashback Engine: Design a cashback calculator where: UPI payments ≥₹500 get 2% cashback, Credit card payments get 1%, Paytm Wallet gets 3%. Apply a max cashback cap of ₹100. Use a combination of switch (payment method) and if-else (amount threshold).

I2. Swiggy Delivery Fee Calculator: Build a program where delivery fee depends on: distance (<3 km → Free, 3-7 km → ₹25, 7-12 km → ₹50, 12+ km → ₹75), time of day (peak hours 12-2 PM and 7-10 PM add ₹15 surge), and membership (Swiggy One members get free delivery under 10 km).

I3. CRED Score Evaluator: Write a program that takes a credit score (300-900) and determines loan eligibility: 750+ → All loans approved at best rates, 650-749 → Personal loan approved with higher interest, 550-649 → Only secured loans, Below 550 → No loans approved. Use nested if-else.

🎯 Interview Questions (3)

IV1. What is the output of this code? (TCS/Wipro favourite):

Java
int x = 2;
switch(x) {
    case 1: System.out.print("A");
    case 2: System.out.print("B");
    case 3: System.out.print("C");
    default: System.out.print("D");
}

IV2. Can you use long, float, or boolean in a switch expression? Explain why or why not.

IV3. Rewrite this nested if-else as a switch expression (Java 14+):

Java
String status;
if (code == 200) status = "OK";
else if (code == 404) status = "Not Found";
else if (code == 500) status = "Server Error";
else status = "Unknown";

MCQ Assessment Bank — 30 Questions (Bloom's Mapped)

Remember / Identify (Q1–Q5)

Understand / Explain (Q6–Q10)

Apply / Implement (Q11–Q15)

int x = 5;
if (x > 3)
    if (x > 7)
        System.out.print("A");
    else
        System.out.print("B");
else
    System.out.print("C");

int val = 1;
switch(val) {
    case 1: System.out.print("One");
    case 2: System.out.print("Two");
    case 3: System.out.print("Three");
    default: System.out.print("Default");
}

char ch = 'B';
switch(ch) {
    case 'A': case 'E': case 'I':
        System.out.print("Vowel"); break;
    default:
        System.out.print("Consonant");
}

int marks = 75;
if (marks >= 90) System.out.print("A");
else if (marks >= 80) System.out.print("B");
else if (marks >= 70) System.out.print("C");
else if (marks >= 60) System.out.print("D");
else System.out.print("F");

String result = switch(3) {
    case 1 -> "One";
    case 2, 3 -> "Two or Three";
    default -> "Other";
};
System.out.println(result);

Analyze / Compare (Q16–Q20)

int n = 2;
switch(n) {
    case 1: System.out.print("A");
    case 2: System.out.print("B");
    case 3: System.out.print("C"); break;
    case 4: System.out.print("D");
    default: System.out.print("E");
}

int a = 10, b = 20;
if (a > b)
    System.out.print("X");
    System.out.print("Y");

Evaluate / Judge (Q21–Q25)

switch(grade) {
    case "A": System.out.println("Excellent");
    case "B": System.out.println("Good");
    case "A": System.out.println("Outstanding");
}

int x = 5;
switch(x) {
    default: System.out.print("D");
    case 1: System.out.print("A"); break;
    case 2: System.out.print("B");
}

// Option A: if-else
if(choice==1) {...}
else if(choice==2) {...}
else if(choice==3) {...}

// Option B: switch
switch(choice) {
  case 1: ...break;
  case 2: ...break;
  case 3: ...break;
}

Create / Design (Q26–Q30)

int x = 0;
switch(x) {
    case 0: System.out.print("Zero");
    default: System.out.print("Def"); break;
    case 1: System.out.print("One");
}

Short Answer Questions (8)

Java
int n = 1;
switch(n) {
    case 1: System.out.print("A"); // matches, prints A
    case 2: System.out.print("B"); // falls through, prints B
    case 3: System.out.print("C"); // falls through, prints C
}
// Output: ABC (not just A!)

Java
if (x > 0)          // outer if
    if (x > 100)     // inner if
        print("Big");
    else             // belongs to inner if (nearest), NOT outer!
        print("Small");
// Solution: ALWAYS use braces {}

Java
switch(x) {
    default: System.out.println("Always executes");
}

Long Answer Questions (3)

Lab Programs

All lab exercises for this unit are integrated into Section D (Learn by Doing) as a 3-tier lab structure. The labs use the IRCTC Fare Calculator as the unifying project, progressively building complexity from basic if-else (Tier 1) through switch-case (Tier 2) to a complete booking system (Tier 3).

Industry Spotlight — A Day in the Life

Earn With It — Rule-Based Calculator Apps

Chapter Summary

📱 Code Tweet (Summary in 280 Characters)

Earning Checkpoint — Self-Assessment

✅ Unit 4 complete. MCQs: 30. Ready for Unit 5!

[QR: Link to EduArtha video tutorial — Java Conditional Statements]