Last modified: January 07, 2023

Math in Java

Basic Math Operators

The basic math methods in Java look identical to the ones from JavaScript.

Addition: +

Subtraction: -

When you need to plus something by one, instead of "something += 1", you can write "something++" or "++something". Similarly, when you need to subtract something by one, instead of "something -= 1", you can write "something--" or "--something".

Multiplication: *

Division: /

Modulus: %

Be careful about division. Compare these 2 examples below:

public class BeCarefulAboutDivision {
    public static void main(String[] args){
        double a = 3.0;
        double b = 2.0;
        System.out.println(a / b);
    }
}

public class BeCarefulAboutDivision {
    public static void main(String[] args){
        int a = 3;
        int b = 2;
        System.out.println(a / b);
    }
}

When we run the first program, 1.5 is printed out. However, when we run the second program, 1 is printed out.

Why the second one printed out 1 instead of 1.5 In Java, a division between two integers must result in integer. Although 3 / 2 should have been 1.5, Java forces it into an integer, and 1.5 became 1.

To make the second program also print out 1.5, we can convert a or b to be doubles so that their division can result in a double:

public class BeCarefulAboutDivision {
    public static void main(String[] args){
        int a = 3;
        int b = 2;
        System.out.println((double)a / b);
    }
}

This process of converting one data type into another is called typecasting.

The Math Class

In addition to the basic math above, Java also provides several built-in methods for you to perform other convenient math operations, such as: