Multiply/divide

Add multiply, divide and zero check.

multiply and divide

We'll add multiplication and division methods to the calculator. multiply multiplies two numbers, divide divides the first by the second.

static int multiply(int a, int b) {
    return a * b;
}
static int divide(int a, int b) {
    if (b == 0) {
        return 0;
    }
    return a / b;
}

divide has a divide by zero check: if b is zero, the method returns 0. This prevents the program from crashing. Java normally throws ArithmeticException when you try to divide by zero.

Exercise Add multiply and divide methods

Add static int multiply(int a, int b) and static int divide(int a, int b) methods to the existing class. multiply returns a * b, divide returns a / b with a zero check. Print multiply(5, 3) and divide(10, 2) in main with println; keep the existing calls.

Show example solution

public class Main {
    static int add(int a, int b) {
        return a + b;
    }
    static int subtract(int a, int b) {
        return a - b;
    }
    static int multiply(int a, int b) {
        return a * b;
    }
    static int divide(int a, int b) {
        if (b == 0) {
            return 0;
        }
        return a / b;
    }
    public static void main(String[] args) {
        System.out.println("Calculator");
        System.out.println(add(5, 3));
        System.out.println(subtract(5, 3));
        System.out.println(multiply(5, 3));
        System.out.println(divide(10, 2));
    }
}

Division by zero

Integer division by zero throws ArithmeticException in Java. This stops the program and shows an error to the user.

To prevent this, our divide method checks b == 0 and safely returns 0. This is called defensive guarding.

In the next lesson we'll do the same with try/catch. That's another way to catch the error.

Test yourself

Complete the multiply return

static int multiply(int a, int b) { return a ____ b; }

Show answer

static int multiply(int a, int b) { return a * b; }

Match the operations

add

Addition
subtract

Subtraction
multiply

Multiplication
divide

Division
What does divide(10, 0) return in this code?
- 0
- Throws an error
- 10
- 1
Show answer

0 — The zero check returns 0, no error.

Next lesson: Error handling

We Are Enhancing Your Experience

Cookie Preferences

Strictly Necessary Cookies

Analytical Cookies