Arithmetic operators in Java

Introduction

Arithmetic operators help you do math with numbers in your program. They let you add, subtract, multiply, divide, and find remainders easily.

Calculating the total price of items in a shopping cart.

Finding the average score of a student.

Counting how many days are left until an event.

Splitting a bill evenly among friends.

Converting units, like inches to centimeters.

Syntax

Java

result = value1 + value2;  // addition
result = value1 - value2;  // subtraction
result = value1 * value2;  // multiplication
result = value1 / value2;  // division
result = value1 % value2;  // remainder (modulus)

Use + to add numbers.

Use % to get the remainder after division.

Examples

Adds 5 and 3 to get 8.

Java

int sum = 5 + 3;  // sum is 8

Subtracts 4 from 10 to get 6.

Java

int difference = 10 - 4;  // difference is 6

Multiplies 7 by 2 to get 14.

Java

int product = 7 * 2;  // product is 14

Divides 20 by 5 to get 4, and finds remainder of 20 divided by 3 which is 2.

Java

int quotient = 20 / 5;  // quotient is 4
int remainder = 20 % 3;  // remainder is 2

Sample Program

This program shows how to use all the basic arithmetic operators with two numbers, 15 and 4. It prints the results of each operation.

Java

public class ArithmeticOperatorsDemo {
    public static void main(String[] args) {
        int a = 15;
        int b = 4;

        int sum = a + b;
        int difference = a - b;
        int product = a * b;
        int quotient = a / b;
        int remainder = a % b;

        System.out.println("Sum: " + sum);
        System.out.println("Difference: " + difference);
        System.out.println("Product: " + product);
        System.out.println("Quotient: " + quotient);
        System.out.println("Remainder: " + remainder);
    }
}

Important Notes

Division between two integers gives an integer result, cutting off any decimal part.

Use parentheses () to control the order of operations if needed.

Summary

Arithmetic operators let you do basic math in Java.

They include +, -, *, /, and %.

Remember integer division drops decimals.

Practice

1. Which of the following is the correct symbol for the modulus operator in Java, which gives the remainder of a division?

easy

A. *

B. /

C. -

D. %

Solution

1. Step 1: Understand the modulus operator

   The modulus operator returns the remainder after division of two numbers.

2. Step 2: Identify the correct symbol in Java

   In Java, the symbol for modulus is %.

3. Final Answer:

   % -> Option D

4. Quick Check:

   Modulus operator = % [OK]

Hint: Modulus operator is always % in Java math [OK]

Common Mistakes:

• Confusing modulus % with division /
• Using * or - instead of %
• Thinking modulus returns quotient

2. Which of the following Java statements correctly calculates the product of two integers a and b?

easy

A. int result = a / b;

B. int result = a + b;

C. int result = a * b;

D. int result = a % b;

Solution

1. Step 1: Identify the multiplication operator

   In Java, the multiplication operator is *.

2. Step 2: Check the statement that uses multiplication

   The statement int result = a * b; correctly multiplies a and b.

3. Final Answer:

   int result = a * b; -> Option C

4. Quick Check:

   Multiplication operator = * [OK]

Hint: Use * for multiplication in Java expressions [OK]

Common Mistakes:

• Using + instead of * for multiplication
• Confusing division / with multiplication
• Using % which is remainder, not product

3. What is the output of the following Java code?

int x = 10;
int y = 3;
System.out.println(x / y);

medium

A. 3

B. 3.3333333

C. 3.0

D. 4

Solution

1. Step 1: Understand integer division in Java

   Both x and y are integers, so division drops the decimal part.

2. Step 2: Calculate integer division result

   10 divided by 3 is 3.333..., but integer division returns 3.

3. Final Answer:

   3 -> Option A

4. Quick Check:

   Integer division drops decimals = 3 [OK]

Hint: Integer division drops decimals, result is integer [OK]

Common Mistakes:

• Expecting decimal output with int division
• Confusing / with % operator
• Assuming automatic float conversion

4. Identify the error in the following Java code snippet:

int a = 5;
int b = 0;
int c = a / b;
System.out.println(c);

medium

A. Division by zero causes runtime error

B. Variable c is not declared

C. Missing semicolon after declaration

D. Incorrect use of modulus operator

Solution

1. Step 1: Analyze the division operation

   The code divides a by b, where b is zero.

2. Step 2: Understand division by zero in Java

   Dividing an integer by zero causes a runtime ArithmeticException error.

3. Final Answer:

   Division by zero causes runtime error -> Option A

4. Quick Check:

   Division by zero throws error [OK]

Hint: Never divide by zero; it crashes the program [OK]

Common Mistakes:

• Ignoring division by zero error
• Thinking it returns zero or infinity
• Confusing syntax error with runtime error

5. Given the code below, what will be the value of result after execution?

int a = 15;
int b = 4;
int result = a / b + a % b * 2;

hard

A. 11

B. 9

C. 8

D. 7

Solution

1. Step 1: Calculate integer division and modulus

   15 / 4 = 3 (integer division), 15 % 4 = 3 (remainder).

2. Step 2: Apply operator precedence and compute expression

   Expression is 3 + 3 * 2. Multiplication first: 3 * 2 = 6. Then addition: 3 + 6 = 9.

3. Step 3: Re-check calculation

   Wait, re-check: 15 / 4 = 3, 15 % 4 = 3, 3 * 2 = 6, 3 + 6 = 9.

4. Final Answer:

   9 -> Option B

5. Quick Check:

   Division + (modulus * 2) = 9 [OK]

Hint: Remember * before + in mixed expressions [OK]

Common Mistakes:

• Adding before multiplying
• Confusing division and modulus results
• Forgetting integer division truncates decimals