Primes.java

import java.util.InputMismatchException;
import java.util.Scanner;

// this class will return the nth prime number, where n is a positive integer (or zero) input by the user

public class Primes {

	public static void main(String[] args) {

		var scanner = new Scanner(System.in);
		int n=-1;
		int counter=-1;
		int i=2;

		while (true) {
            System.out.print("Enter a number: ");
            try {
            	n = scanner.nextInt();	// prompt the user to enter a number
            	if (n > -1) {
                    break;  // if an integer greater than -1 is inputed, we break the loop
                }
                System.out.println("Invalid input, please enter a positive number or 0."); // if an integer less than zero is inputed, the loop will not be broken and this line will be printed
            } catch(InputMismatchException e) { // enter this catch block if a non integer is input
            	System.out.println("Invalid input, input must be an integer");
            	scanner.next(); // call scanner.next() to prevent an infinite loop
            }
        }
		scanner.close();

		while(counter<n) {	// iterate through the set of natural numbers counting how many prime numbers are encountered
			if (isPrime(i)) {
				counter++;
			}
			i++;
		}
		System.out.println(i-1);

	}

	public static boolean isPrime (double x) {		// a method to detect whether a number is prime or not

		for (int i=2; i<(x/2)+1; i++) {		// loop over all natural numbers that precede the number that you are checking to be prime or not

			if (x % i == 0)	{	// if the number is found to be divisible by a natural number that proceeds it, the number is not prime
				return false;
			}
		}
		return true;	// else, the number is prime

	}

}