Arithmetic Operators

Perform calculations in Java using addition, subtraction, multiplication, division, modulus, and increment/decrement operators.

Overview

Arithmetic operators let you perform mathematical calculations in Java. The five basic ones (+, -, *, /, %) work on numeric types. Java also has two shorthand operators - ++ (increment) and -- (decrement) - that add or subtract 1 from a variable. Integer division (dividing two ints) drops the decimal part: 7 / 2 = 3, not 3.5. To get a decimal result, cast one operand to double first. The modulus operator (%) returns the remainder after division and is useful for checking divisibility.

Key Points

•+ addition, - subtraction, * multiplication, / division, % modulus (remainder)
•Integer division truncates: 7 / 2 = 3 (not 3.5); use (double) cast to get decimals
•% modulus: 7 % 3 = 1 (remainder); n % 2 == 0 means n is even
•++ increments by 1: i++ (post-increment) vs ++i (pre-increment)
•-- decrements by 1: i-- (post) vs --i (pre)
•Operator precedence: * / % before + - ; use parentheses to control order

Examples

Basic arithmetic

public class Main {
    public static void main(String[] args) {
        int a = 17, b = 5;

        System.out.println(a + b);  // 22
        System.out.println(a - b);  // 12
        System.out.println(a * b);  // 85
        System.out.println(a / b);  // 3  ← integer division!
        System.out.println(a % b);  // 2  ← remainder

        // Get a decimal result from two ints
        System.out.println((double) a / b); // 3.4
    }
}

17 / 5 = 3 (remainder 2). The decimal .4 is discarded in integer division.

Increment and decrement

public class Main {
    public static void main(String[] args) {
        int x = 5;
        System.out.println(x++); // 5 - prints THEN increments
        System.out.println(x);   // 6

        int y = 5;
        System.out.println(++y); // 6 - increments THEN prints
        System.out.println(y);   // 6

        int z = 10;
        z--;
        System.out.println(z);   // 9
    }
}

Post-increment (x++) returns the old value. Pre-increment (++x) returns the new value.

Operator precedence and parentheses

public class Main {
    public static void main(String[] args) {
        System.out.println(2 + 3 * 4);    // 14 (* before +)
        System.out.println((2 + 3) * 4);  // 20 (parentheses first)

        // Compound interest: A = P * (1 + r)^n  (simplified)
        double p = 1000, r = 0.05;
        int n = 3;
        double amount = p * Math.pow(1 + r, n);
        System.out.printf("Amount: %.2f%n", amount); // 1157.63
    }
}

Always use parentheses when you're unsure about precedence - it makes intent explicit.

Common Mistakes

Integer division: expecting 5 / 2 to be 2.5 - it is 2 in Java (both operands are int)
Division by zero with ints: `int x = 5 / 0` throws ArithmeticException; double division gives Infinity
Confusing x++ with ++x in expressions where the return value matters

Note

Use Math.pow(base, exponent) for exponentiation - Java has no ** operator like Python.

Arithmetic Operators

Overview

Key Points

Examples

Common Mistakes

Note

Exercises

Knowledge Check

What is the result of `7 / 2` in Java when both 7 and 2 are int?