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.");
        }
    }
}
Main.main(null);

You are an adult and a student.

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.");
        }
    }
}
Main.main(null);

You are an adult and 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();

Purpose of the Algorithm
The checkMembershipEligibility function determines if a user qualifies for different memberships or discounts based on their age, annual income, and student status.

Explanation of Each If Condition
Basic Membership: Checks if the user is 18+ years old and has an income of $20,000+. If true, they qualify.
Premium Membership: Checks if the user is 25+ years old and has an income of $50,000+. If true, they qualify.
Student Discount: Checks if the user is a student. If true, they qualify.
Senior Discount: Checks if the user is 65+ years old. If true, they qualify.
Default Message: If no qualifications are met, it indicates the user does not qualify for any memberships or discounts.

Input:
Age: 20
Annual Income: 1500
Student Status: Yes
Output:
You are eligible for a Student Discount.

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

        // Compound conditional logic to determine discount eligibility
        if (age < 18 || isStudent) {
            System.out.println("You qualify for a discount!");
        } else {
            System.out.println("You do not qualify for a discount.");
        }
    }
}
Main.main(null);

You qualify for a discount!

Unit 3 Team Teach - 3.5 Compound Booleans

Unit 3 Team Teach