Arithmetic operators in Java - Cheat Sheet & Quick Revision

Recall & Review

beginner

What are arithmetic operators in Java?

Arithmetic operators are symbols used to perform basic math operations like addition (+), subtraction (-), multiplication (*), division (/), and modulus (%).

beginner

What does the modulus operator (%) do?

The modulus operator (%) gives the remainder after dividing one number by another. For example, 7 % 3 equals 1 because 7 divided by 3 leaves a remainder of 1.

beginner

What is the result of integer division in Java?

When dividing two integers, Java returns the quotient without the decimal part. For example, 7 / 3 equals 2, not 2.333.

beginner

How do you perform multiplication in Java?

Use the asterisk (*) symbol between two numbers. For example, 4 * 5 equals 20.

intermediate

What happens if you divide by zero in Java?

Dividing an integer by zero causes a runtime error called ArithmeticException. Dividing a floating-point number by zero results in Infinity or NaN.

Which operator is used for addition in Java?

A *

B +

C -

D %

The plus sign (+) is used for addition.

What is the output of 10 % 4 in Java?

A 6

B 0

C 2

D 4

10 divided by 4 leaves a remainder of 2, so 10 % 4 equals 2.

What is the result of 9 / 2 when both are integers?

A 4

B 4.5

C 5

D 2

Integer division truncates the decimal, so 9 / 2 equals 4.

Which operator multiplies two numbers?

A -

B +

C /

D *

The asterisk (*) is used for multiplication.

What happens if you divide an integer by zero in Java?

A Throws ArithmeticException

B Returns Infinity

C Returns zero

D Returns NaN

Dividing an integer by zero throws an ArithmeticException at runtime.

Explain the difference between division and modulus operators in Java.

Think about what happens when you divide numbers and what is left over.

Describe what happens when you use arithmetic operators on integers versus floating-point numbers in Java.

Consider how Java treats whole numbers and decimals differently.

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