Check Odd Number in Java
What you’ll learn
- How to check odd numbers using
n % 2 != 0. - How this rule works for positive, zero, and negative integers.
- How to print odd numbers in a range with a simple loop.
Prerequisites
Integers, modulo operator, and simple if-else flow.
- Java
intand%basics. - Parity idea: every integer is either even or odd.
What is an odd number?
An integer is odd when divided by 2 gives a non-zero remainder. In Java, use n % 2 != 0.
Math definition
An integer n is odd iff n = 2k + 1 for some integer k. Equivalent program check: n % 2 != 0.
Intuition and examples
15 % 2 = 1 so odd; 18 % 2 = 0 so not odd.
Live preview
Algorithm
Compute n % 2; non-zero means odd.
📜 Pseudocode
Pseudocode
if n % 2 != 0:
odd
else:
not odd1
Check one number
java
public class Main {
static boolean isOdd(int number) {
return number % 2 != 0;
}
public static void main(String[] args) {
int number = 15;
if (isOdd(number)) {
System.out.println(number + " is an odd number.");
} else {
System.out.println(number + " is not an odd number.");
}
}
}2
Print odds from 1 to 10
java
public class Main {
static void printOddNumbersFrom1To10() {
System.out.println("Odd numbers in the range 1 to 10:");
for (int i = 1; i <= 10; i++) {
if (i % 2 != 0) {
System.out.print(i + " ");
}
}
System.out.println();
}
public static void main(String[] args) {
printOddNumbersFrom1To10();
}
}Optimization
Single parity check is already constant-time; focus on readability.
❓ FAQ
A whole number not divisible by 2 is odd.
No. Zero is even.
Because odd numbers leave nonzero remainder when divided by 2.
Yes. Negative odd numbers also satisfy n % 2 != 0.
For integers, yes.
Single check O(1); scanning range O(k).
🔄 Input / output examples
n = 15 -> odd, n = 0 -> not odd, n = -3 -> odd.
Edge cases
Zero is even; negative odd numbers are valid odd integers.
⏱️ Time and space complexity
Single check O(1), range print O(k).
Summary
- Use
n % 2 != 0for odd check in Java. - Runs in constant time for one number.
Did you know?
Every integer is either even or odd. Zero is even, so it is not odd.
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