write bluej program to input a number and check it is a prime or not if not a prime number then print the next prime number
using Scanner
Answers
Finding Next Closest Prime - Java
BlueJ is an IDE developed for beginners to use Java. We will be writing the program in Java.
We take the User Input first of all. Now, we need to check if this number is a Prime or not. For that, we create a function static boolean isPrime(int number), which would return true if the number is prime and false if it is not.
In the function, we check divisibility by each number from 2 to the square root of user number. If divisibility is found, return false. If no divisibility is found, number is prime and so return true.
If the user input number is prime, simply print it out. Else, initialize another variable with the same value, and keep incrementing it until we get a Prime.
Here's a code which works as required.
import java.util.Scanner; //Importing Scanner
public class NextPrime
{
//Function to check if a number is Prime or not
static boolean isPrime(int number)
{
//Check divisibility from 2 to sqrt(number)
for(int i=2; i<=(int)Math.sqrt(number); i++)
{
if(number % i == 0)
{
//If divisibility is found, number is not prime
return false;
}
}
//If no divisibility is found, number is prime
return true;
}
public static void main(String[] args) //main function
{
Scanner sc = new Scanner(System.in); //Create Scanner object
//Take User Input
System.out.print("Enter a number: ");
int num = sc.nextInt();
if(isPrime(num)) //Calling function
{
//If number is Prime, simply print it out
System.out.println(num+" is a Prime.");
}
else
{
//If user number is not prime, we need to find the next prime
int nextPrime = num; //Initialising nextPrime as num
//Run a loop until a prime is found
while(!isPrime(nextPrime))
{
nextPrime++; //Incrementing by 1
}
//Print out the relevant stuff
System.out.println(num+" is not a prime. The Next Prime is: "+nextPrime);
}
}
}
Explanation:
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