3.5 Compund Boolean expressions

Nested conditional statements

definition: if statements within other if statements

public class Main {
    public static void main(String[] args) {
        int age = 20;
        boolean isStudent = true;

        // Outer if-else block
        if (age >= 18) {
            // Nested if-else block inside the first condition
            if (isStudent) {
                System.out.println("You are an adult and a student.");
            } else {
                System.out.println("You are an adult.");
            }
        } else {
            System.out.println("You are not an adult.");
        }
    }
}

Simple Example of a Nested Conditional Statement

Let’s look at a very basic example of a nested conditional statement using if-else blocks.

Scenario:

We want to check if a person is an adult and, if they are, we want to know if they are also a student.

Compound Conditional Statement

A compound conditional statement is when two or more conditions are combined into a single if statement using logical operators like && (AND), || (OR), or ! (NOT). This allows us to check multiple conditions at once without needing to nest if statements.

Logical Operators:

&& (AND): True if both conditions are true.
|| (OR): True if at least one condition is true.
! (NOT): Reverses the result of a condition (true becomes false, and false becomes true).

Example of a Compound Conditional Statement

Let’s say we want to check if a person is an adult and a student at the same time. Instead of using a nested if statement, we can use a compound conditional statement.

public class Main {
    public static void main(String[] args) {
        int age = 20;
        boolean isStudent = true;

        // Compound conditional using && (AND)
        if (age >= 18 && isStudent) {
            System.out.println("You are an adult and a student.");
        } else {
            System.out.println("Either you are not an adult, or you are not a student.");
        }
    }
}

common mistake: Dangling else

- Java does not care about indentation
- else always belongs to the CLOSEST if
- curly braces can be use to format else so it belongs to the FIRST 'if'

Popcorn hack

explain the purpose of this algorithm, and what each if condition is used for
what would be output if input is
- age 20
- anual income 1500
- student status: yes

function checkMembershipEligibility() {
    // Get user input
    let age = parseInt(prompt("Enter your age:"));  // Age input
    let income = parseFloat(prompt("Enter your annual income:"));  // Annual income input
    let isStudent = prompt("Are you a student? (yes/no):").toLowerCase() === 'yes';  // Student status input

    // Initialize an empty array to hold results
    let results = [];

    // Check eligibility for different memberships

    // Basic Membership
    if (age >= 18 && income >= 20000) {
        results.push("You qualify for Basic Membership.");
    }

    // Premium Membership
    if (age >= 25 && income >= 50000) {
        results.push("You qualify for Premium Membership.");
    }

    // Student Discount
    if (isStudent) {
        results.push("You are eligible for a Student Discount.");
    }

    // Senior Discount
    if (age >= 65) {
        results.push("You qualify for a Senior Discount.");
    }

    // If no eligibility, provide a default message
    if (results.length === 0) {
        results.push("You do not qualify for any memberships or discounts.");
    }

    // Output all results
    results.forEach(result => console.log(result));
}

// Call the function to execute
checkMembershipEligibility();

|       let isStudent = prompt("Are you a student? (yes/no):").toLowerCase() === 'yes';  // Student status input

illegal start of expression

|       let isStudent = prompt("Are you a student? (yes/no):").toLowerCase() === 'yes';  // Student status input

unclosed character literal

|       let isStudent = prompt("Are you a student? (yes/no):").toLowerCase() === 'yes';  // Student status input

unclosed character literal

|       let isStudent = prompt("Are you a student? (yes/no):").toLowerCase() === 'yes';  // Student status input

not a statement

|       let results = [];

illegal start of expression

|       if (results.length === 0) {

illegal start of expression

|       results.forEach(result => console.log(result));

illegal start of expression

the output would be “You are eligible for a Student Discount.”; the purpose of this hack is to check the membership eligibility based on a set of criteria.

Popcorn Hack #2

Write a program that checks if a person can get a discount based on their age and student status. You can define your own discount criteria! Use compound conditionals to determine the output.

public class Main {
    public static void main(String[] args) {
        int age = 30; // Change this value for testing
        boolean isStudent = true; // Change this value for testing

        // Your compound conditional logic here
    }
}

public class Main {
    public static void main(String[] args) {
        int age = 30; // Change this value for testing
        boolean isStudent = true; // Change this value for testing

        // Compound conditional logic for discount criteria
        if (age < 18) {
            System.out.println("Eligible for a 50% discount.");
        } else if (age >= 65) {
            System.out.println("Eligible for a 30% discount.");
        } else if (isStudent) {
            System.out.println("Eligible for a 20% student discount.");
        } else {
            System.out.println("No discount available.");
        }
    }
}

Unit 3 Team Teach - 3.5 Compound Booleans

Unit 3 Team Teach