Module 3: Operators, Expressions, and Strings

Arithmetic and Assignment Operators

Use `+`, `-`, `*`, `/`, `%`, and assignment operators to update values and calculate results.

Author

Java Learner Editorial Team

Reviewer

Technical review by Java Learner

Last reviewed

2026-04-16

Java version

Java 25 LTS

How this lesson was prepared: AI-assisted draft, edited by hand, and checked against current Java 25 documentation and runnable examples.

Learning goals

Use the main arithmetic operators correctly
Update variables with assignment
Read short math expressions in Java

Arithmetic operators: Use +, -, *, /, and % for addition, subtraction, multiplication, division, and remainder.

Assignment operators: = stores a value in a variable. Variants such as += and -= update the variable using its current value.

Integer division warning: 7 / 2 with integers gives 3, not 3.5. Use a double if you need decimal precision.

Why this matters: Most beginner projects use arithmetic long before they use classes or frameworks.

Runnable examples

Basic arithmetic

public class Main {
    public static void main(String[] args) {
        int a = 10;
        int b = 3;
        System.out.println(a + b);
        System.out.println(a % b);
    }
}

Expected output

13
1

Update with assignment

public class Main {
    public static void main(String[] args) {
        int score = 10;
        score += 5;
        score -= 2;
        System.out.println(score);
    }
}

Expected output

Common mistakes

Expecting integer division to keep decimals

Use a `double` value in the expression if you need decimal results.

Mini exercise

Create a price variable, add tax to it with `+=`, and print the final value.

Summary

Arithmetic changes values.
Assignment stores or updates values.
Integer division behaves differently from decimal division.

Next step

Next, compare values and combine conditions with logical operators.

Sources used

Arithmetic and Assignment Operators

Basic arithmetic

Update with assignment

What does `10 % 4` return?