Conditional Statements

The if statement

The if statement runs code based on a condition.

java

public class Main {
    public static void main(String[] args) {
        boolean isMembershipActive = true;

        if (isMembershipActive) {
            System.out.println("Member can borrow books.");
        }
    }
}

output

Member can borrow books.

The else statement

The else statement executes a block of code when the condition in the if statement is false.

java

public class Main {
    public static void main(String[] args) {
        boolean isMembershipActive = false;

        if (isMembershipActive) {
            System.out.println("Member can borrow books.");
        } else {
            System.out.println("Membership is inactive. Please renew.");
        }
    }
}

output

Membership is inactive. Please renew.

The else if statement

The else if statement allows us to perform additional checks.

java

public class Main {
    public static void main(String[] args) {
        int userAge = 25;

        if (userAge < 18) {
            System.out.println("User is a minor.");
        } else if (userAge >= 18 && userAge <= 65) {
            System.out.println("User is an adult.");
        } else {
            System.out.println("User is a senior.");
        }
    }
}

output

User is an adult.

The ternary operator

The ternary operator provides a shorthand way of writing conditional expressions. It has three operands, separated by a question mark ? and a colon :.

condition ? (runs if condition true) : (runs if condition false);

We could use this to concisely check book availability:

java

public class Main {
    public static void main(String[] args) {
        int availableBooks = 3;

        String message = availableBooks > 0 ? "Books are available." : "Books are out of stock.";

        System.out.println(message);
    }
}

output

Books are available.