Java If Else

Every useful program has to make decisions. Should the heater turn on? Did the student pass? Does this order get free shipping? In Java, you make decisions with the if else statement. In this lesson, you'll learn how Java if else works, how to chain several choices with else if, when to nest one if inside another, and which small mistakes cause the biggest headaches.

What is an if statement in Java?

An if statement runs a block of code only when a condition is true. The condition goes inside parentheses and must be a boolean expression, which means something that is either true or false, such as temperature < 19. The code to run goes inside curly braces { }, which form a block.

if (condition) {
    // runs only when condition is true
}

Here's a complete program. Try changing temperature to 22 and run it again.

public class Thermostat {
    public static void main(String[] args) {
        int temperature = 16;

        if (temperature < 19) {
            System.out.println("It's chilly. Heating ON.");
        }

        System.out.println("Thermostat check complete.");
    }
}

It's chilly. Heating ON.
Thermostat check complete.

The last line always prints, because it sits outside the if block. Only the line inside the braces depends on the condition. The conditions themselves use the comparison operators you already know: <, >, <=, >=, == and !=.

How do you add an else block?

Often you want to do one thing when the condition is true and something different when it's false. That's what else is for. Exactly one of the two blocks runs, never both and never neither.

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

        if (failedAttempts >= 3) {
            System.out.println("Account locked. Please reset your password.");
        } else {
            System.out.println("You can try again.");
        }
    }
}

Account locked. Please reset your password.

Using else if for more than two choices

When there are three or more possible paths, chain them with else if. Java tests each condition from top to bottom. As soon as one is true, it runs that block and skips the rest of the chain. The final else is optional and catches everything that didn't match.

public class ThermostatModes {
    public static void main(String[] args) {
        int temperature = 26;

        if (temperature < 19) {
            System.out.println("Mode: HEATING");
        } else if (temperature > 24) {
            System.out.println("Mode: COOLING");
        } else {
            System.out.println("Mode: IDLE");
        }
    }
}

Mode: COOLING

Why does the order of conditions matter?

Because Java stops at the first true condition, the order of your else if branches changes the result. A grading program is the classic example. Start with the highest score and work down:

public class GradeBook {
    public static void main(String[] args) {
        int score = 84;
        char grade;

        if (score >= 90) {
            grade = 'A';
        } else if (score >= 80) {
            grade = 'B';
        } else if (score >= 70) {
            grade = 'C';
        } else if (score >= 60) {
            grade = 'D';
        } else {
            grade = 'F';
        }

        System.out.println("Score " + score + " earns a " + grade);
    }
}

Score 84 earns a B

A score of 84 fails the first test (84 >= 90) and passes the second, so the grade is B. Java never even looks at the >= 70 branch. If you had put score >= 60 first, every passing student would get a D!

Notice also that grade is declared before the chain without a value. That's fine, because the final else guarantees one branch always assigns it. Remove the else and the compiler complains that grade "might not have been initialized".

Combining conditions with && and ||

One condition can check several things at once using the logical operators: && (and), || (or) and ! (not).

public class RideCheck {
    public static void main(String[] args) {
        int heightCm = 128;
        boolean withAdult = true;

        if (heightCm >= 140 || (heightCm >= 120 && withAdult)) {
            System.out.println("Enjoy the roller coaster!");
        } else {
            System.out.println("Sorry, not tall enough yet.");
        }
    }
}

Enjoy the roller coaster!

What is a nested if statement?

A nested if is an if statement placed inside another if or else block. Use it when the second question only makes sense after the first one is answered. For example, a store might first ask "is this a domestic order?" and only then look at the order total.

public class ShippingCost {
    public static void main(String[] args) {
        boolean domestic = true;
        double orderTotal = 42.50;
        double shipping;

        if (domestic) {
            if (orderTotal >= 50) {
                shipping = 0.0;
            } else {
                shipping = 4.99;
            }
        } else {
            shipping = 19.99;
        }

        System.out.println("Order total: $" + orderTotal);
        System.out.println("Shipping:    $" + shipping);
        System.out.println("You pay:     $" + (orderTotal + shipping));
    }
}

Order total: $42.5
Shipping:    $4.99
You pay:     $47.49

Indent each nested level by four spaces so you can see at a glance which else belongs to which if. If you find yourself three or four levels deep, it's usually clearer to flatten the logic into an else if chain with &&.

Do you always need curly braces?

Technically, no. If an if or else block contains a single statement, Java lets you leave out the braces:

if (score >= 60) System.out.println("Passed");
else System.out.println("Try again");

But it's a trap. Without braces, only the first statement belongs to the if. Look at this program, where the indentation lies about what the code does:

public class MissingBraces {
    public static void main(String[] args) {
        int balance = 500;

        if (balance < 100)
            System.out.println("Low balance warning!");
            System.out.println("Sending alert email...");

        System.out.println("Balance: " + balance);
    }
}

Sending alert email...
Balance: 500

The balance is fine, yet the alert email line still runs, because it was never part of the if. Most professional teams have a simple rule: always use braces, even for one line.

How do you compare Strings in an if?

Use .equals(), not ==. As you saw in Java string comparison, == checks whether two variables point to the same object, not whether the text matches.

public class CouponCheck {
    public static void main(String[] args) {
        String coupon = "save10";
        double price = 80.0;

        if (coupon.equalsIgnoreCase("SAVE10")) {
            price = price * 0.90;
            System.out.println("Coupon applied!");
        } else {
            System.out.println("Unknown coupon.");
        }
        System.out.println("Price: " + price);
    }
}

Coupon applied!
Price: 72.0

Common mistakes with Java if else

1. Using = instead of ==

A single = assigns; it doesn't compare. Writing if (count = 5) with an int doesn't even compile:

error: incompatible types: int cannot be converted to boolean

Java requires a boolean condition, which saves you from a bug that is common in C.

2. A semicolon right after the condition

if (temperature < 19); {
    System.out.println("Heating ON");   // always runs!
}

The semicolon ends the if statement with an empty body. The block below then runs every time. Never put ; between ) and {.

3. Conditions in the wrong order

In an else if chain, put the most specific (or highest) test first. A broad test at the top swallows every case below it.

4. Comparing Strings with ==

if (answer == "yes") may work in a quick test and then fail with text typed by a user. Always write answer.equals("yes").

Practice exercise

public class CinemaTicket {
    public static void main(String[] args) {
        int age = 70;
        boolean isTuesday = true;
        int price;

        if (age < 12) {
            price = 6;
        } else if (age >= 65) {
            price = 7;
        } else {
            price = 12;
        }

        if (isTuesday) {
            price = price - 2;
        }

        System.out.println("Ticket price: $" + price);
    }
}

Ticket price: $5

What's next?

Long else if chains that compare one variable against many fixed values can get repetitive. Next, learn the Java switch statement, a cleaner way to pick one option out of many.