In this post, we will see how to find nth Prime number in java.

Table of Contents

## What is prime number

Prime number is a number that is greater than 1 and divided by 1 or itself.

**For example:** 5, 7, 13, 23

We have already seen how to check if number is prime or not. We will use same method to find nth prime number in java.

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## Nth prime number in java

Here are steps to find nth prime number in java.

- Take value of
`n`

from user using Scanner class. - Intialize a variable
`count`

. It will keep track of number of prime number processed so far. - Intialize a variable
`i`

. It will keep track of current number. - Iterate over while loop until
`count ! = n`

- Increment
`i`

by 2 as even numbers are not prime - Check if number is prime. If number is prime then increment
`count`

by 1.

- Increment
- Return
`i`

which is nth prime number.

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 |
package org.arpit.java2blog; import java.util.Scanner; public class NthPrimeNumberJava { public static void main(String args[]){ Scanner in = new Scanner(System.in); //Input the value of 'n' System.out.println("Enter the value of n"); int n= in.nextInt(); int nthPrimeNumber = findNthPrimeNumber(n); System.out.println("Nth Prime Number is: "+nthPrimeNumber); } private static int findNthPrimeNumber(int n) { if(n==1) { return 2; } int i=1; int count=1; //While loop should run until we find nth prime number i.e (count != n) while(count != n){ // increment number by 2 as even numbers are always not prime i+=2; if(isPrime(i)) count++; // increment the count when we get prime number } // return nth prime number return i; } public static boolean isPrime(int num) { if (num <= 1) { return false; } for (int i = 2; i <= Math.sqrt(num); i++) { if (num % i == 0) { return false; } } return true; } } |

**Output:**

24

Nth Prime Number is: 89

That’s all about how to find nth prime number in java.