Arithmetic operators in Java - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ Predict Output

intermediate

Output of mixed arithmetic operations

What is the output of the following Java code?

Java

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

A 12

B 9

C 10

D 13

💡 Hint

Remember the order of operations and how integer division works in Java.

Integer division a / b equals 3 (since 10 / 3 = 3). Then 3 * b = 9. The remainder a % b is 1. Adding 9 + 1 gives 10.

❓ Predict Output

intermediate

Result of arithmetic with doubles

What is the output of this Java program?

Java

public class Main {
    public static void main(String[] args) {
        double x = 5.0 / 2;
        double y = 5 / 2.0;
        System.out.println(x + "," + y);
    }
}

A 2.5,2.5

B 2,2

C 2,2.5

D 2.0,2.0

💡 Hint

Check how Java handles division when one operand is a double.

Both divisions involve a double operand, so the division is floating-point, resulting in 2.5 for both.

❓ Predict Output

advanced

Output of complex arithmetic expression with increment operators

What is the output of this Java code snippet?

Java

public class Main {
    public static void main(String[] args) {
        int i = 1;
        int result = i++ + ++i * i++;
        System.out.println(result);
    }
}

A 9

B 12

C 11

D 10

💡 Hint

Evaluate the increments step by step, remembering post-increment and pre-increment behavior.

i++ uses i=1 then increments to 2; ++i increments to 3 then uses 3; i++ uses 3 then increments to 4. Expression: 1 + 3 * 3 = 1 + 9 = 10. Stepwise: i=1; i++=1 (i=2); ++i=3 (i=3); i++=3 (i=4); expression=1 + 3*3=10. Output is 10.

❓ Predict Output

advanced

Division by zero with floating point

What is the output of this Java program?

Java

public class Main {
    public static void main(String[] args) {
        double a = 5.0 / 0;
        System.out.println(a);
    }
}

A ArithmeticException

B Infinity

C NaN

D 0

💡 Hint

Division by zero behaves differently for integers and floating-point numbers in Java.

Dividing a floating-point number by zero results in Infinity, not an exception.

🧠 Conceptual

expert

Number of items in a map after arithmetic key operations

Consider this Java code snippet. How many entries does the map contain after execution?

Java

import java.util.HashMap;
import java.util.Map;

public class Main {
    public static void main(String[] args) {
        Map<Integer, Integer> map = new HashMap<>();
        int x = 2;
        map.put(x + 1, x * 2);
        map.put(x++, x + 3);
        map.put(++x, x * x);
        System.out.println(map.size());
    }
}

A 3

B 2

C 1

D 4

💡 Hint

Track the value of x carefully and note that keys may overwrite existing entries.

Stepwise: x=2 map.put(3,4) // key=3, value=4 map.put(2,5) // x++ uses 2 then x=3, value=5 map.put(4,16) // ++x increments x to 4, value=16 Keys are 3,2,4 distinct, so map size is 3.