From 7227539ca3fe48180564eef025696d23780debfd Mon Sep 17 00:00:00 2001
From: piyushkumar0707 <121piyush466mits@gmail.com>
Date: Sat, 18 Oct 2025 23:14:21 +0530
Subject: [PATCH] feat(programs): add prime number check (basic and sqrt
 optimization)

---
 content/programs/contents.mdx                 | 22 +++--
 .../java-program-to-check-prime-number.mdx    | 99 +++++++++++++++++++
 content/programs/meta.json                    |  1 +
 3 files changed, 112 insertions(+), 10 deletions(-)
 create mode 100644 content/programs/java-program-to-check-prime-number.mdx

diff --git a/content/programs/contents.mdx b/content/programs/contents.mdx
index 582f830f..95aa8e89 100644
--- a/content/programs/contents.mdx
+++ b/content/programs/contents.mdx
@@ -8,13 +8,15 @@ description: A collection of basic Java programs categorized by topic.
 1. [Print an Integer](/programs/print-an-integer)
 2. [Add Two Integers](/programs/add-two-integers)
 3. [Check Even or Odd Number](/programs/check-even-or-odd)
-4. [Add Two Binary](/programs/java-program-to-add-two-binary-numbers)
-5. [Add Two Complex Numbers](/programs/java-program-to-add-two-complex-numbers)
-6. [Multiply Two Numbers](/programs/multiply-two-numbers)
-7. [Check Leap Year](/programs/java-program-to-check-Leap-year)
-8. [Calculate Simple interest](/programs/calculate-simple-interest)
-9. [Check Divisibility](/programs/java-program-to-check-divisbility)
-10. [Calculate Quotient and Reminder](/programs/find-quotient-and-reminder)
-11. [Calculate Power of a Number](/programs/calculate-power-of-a-number)
-12. [Calculate Compound Interest](/programs/calculate-compound-interest)
-13. [Calculate Factorial of a Number](/programs/factorial-in-java)
+4. [Check Prime Number](/programs/java-program-to-check-prime-number)
+5. [Add Two Binary](/programs/java-program-to-add-two-binary-numbers)
+6. [Add Two Complex Numbers](/programs/java-program-to-add-two-complex-numbers)
+7. [Multiply Two Numbers](/programs/multiply-two-numbers)
+8. [Check Leap Year](/programs/java-program-to-check-Leap-year)
+9. [Calculate Simple interest](/programs/calculate-simple-interest)
+10. [Check Divisibility](/programs/java-program-to-check-divisbility)
+11. [Calculate Quotient and Reminder](/programs/find-quotient-and-reminder)
+12. [Calculate Power of a Number](/programs/calculate-power-of-a-number)
+13. [Calculate Compound Interest](/programs/calculate-compound-interest)
+14. [Calculate Factorial of a Number](/programs/factorial-in-java)
+15. [Swap Two Numbers](/programs/swap-two-numbers)
diff --git a/content/programs/java-program-to-check-prime-number.mdx b/content/programs/java-program-to-check-prime-number.mdx
new file mode 100644
index 00000000..3d3ad11a
--- /dev/null
+++ b/content/programs/java-program-to-check-prime-number.mdx
@@ -0,0 +1,99 @@
+---
+title: Java Program to Check Prime Number
+shortTitle: Check Prime Number
+description: Learn how to check whether a number is prime in Java using simple loop-based methods and an optimized square-root approach.
+---
+
+A prime number is a number greater than 1 that has no positive divisors other than 1 and itself. In this article, we’ll implement two approaches to check if a number is prime:
+
+- Basic divisor counting (loop up to n)
+- Optimized method (loop up to √n)
+
+Before you start, you may want to review:
+
+- [Java Variables and Literals](/docs/variables-and-literals)
+- [Java Operators](/docs/operators)
+- [Java Basic Input and Output](/docs/basic-input-output)
+
+## 1) Basic Approach (Loop up to n)
+
+This method is straightforward but less efficient for large n.
+
+### Example
+
+```java
+class Main {
+  public static void main(String[] args) {
+    int n = 29; // change value to test
+
+    if (isPrime(n)) {
+      System.out.println(n + " is a prime number.");
+    } else {
+      System.out.println(n + " is not a prime number.");
+    }
+  }
+
+  static boolean isPrime(int n) {
+    if (n <= 1) return false; // 0, 1, and negatives are not prime
+    int count = 0;
+    for (int i = 1; i <= n; i++) {
+      if (n % i == 0) count++;
+      if (count > 2) return false; // early exit if more than 2 divisors
+    }
+    return count == 2; // exactly two divisors: 1 and n
+  }
+}
+```
+
+#### Output (for n = 29)
+
+```plaintext
+29 is a prime number.
+```
+
+## 2) Optimized Approach (Loop up to √n)
+
+You only need to check divisors up to the square root of n.
+
+### Example
+
+```java
+class Main {
+  public static void main(String[] args) {
+    int n = 30; // change value to test
+
+    if (isPrimeSqrt(n)) {
+      System.out.println(n + " is a prime number.");
+    } else {
+      System.out.println(n + " is not a prime number.");
+    }
+  }
+
+  static boolean isPrimeSqrt(int n) {
+    if (n <= 1) return false;
+    if (n == 2) return true;
+    if (n % 2 == 0) return false; // even numbers > 2 are not prime
+
+    for (int i = 3; i * i <= n; i += 2) {
+      if (n % i == 0) return false;
+    }
+    return true;
+  }
+}
+```
+
+#### Output (for n = 30)
+
+```plaintext
+30 is not a prime number.
+```
+
+---
+
+### Notes & Tips
+
+- Time complexity:
+  - Basic method: O(n)
+  - Optimized method: O(√n)
+- Edge cases: n ≤ 1 (not prime), n = 2 (prime), even numbers > 2 (not prime)
+- For large ranges of numbers, consider the Sieve of Eratosthenes.
diff --git a/content/programs/meta.json b/content/programs/meta.json
index 0279544f..bf6b7da2 100644
--- a/content/programs/meta.json
+++ b/content/programs/meta.json
@@ -17,6 +17,7 @@
 
     "---Conditional Checks---",
     "check-even-or-odd",
+  "java-program-to-check-prime-number",
     "java-program-to-check-divisibility",
     "java-program-to-check-Leap-year",
     "java-program-to-check-whether-input-character-is-vowel-or-consonant",