Here we are explaining how to write a java program to check whether a number is prime or not.
A prime number is a number that can be exactly divided by 1 and that number itself.
Example:2 , 3 ,5, 7 etc.
Here 2 is divided by 1 and 2.
3 is divided by 1 and 3.
5 is divided by 1 and 5.
First, we have to declare the class PrimeNumber with a public modifier. Create an object of the scanner class as sc and read the integer number from the user into the variable num. Create a boolean variable flag and set it to false. By using a for loop
, set i=2and check iN=num/2, Then check the condition for prime, that is check num mod i equals 0 or not. If it equal to zero then set flag=true and break. If
flag not equals true, then display it as a prime number, else
display it as not a prime number using System.out.println()
function.
STEP 1: Declare the class PrimeNumber with a public modifier.
STEP 2: Open the main() to start the program, Java program execution starts with the main()
STEP 3: Read the number from the user into the variable num.
STEP 4: Declare flag as boolean variable and set to false.
STEP 5: By using a for loop
set i=2,check i<=num/2,do step 6.
STEP 6: check if num mod i equals o or not, if it equal to zero then set flag=true and break.
STEP 7: Check if the flag not equal to true then display a number as a prime number.
STEP 8: Else display the number is not a prime number.
import java.util.Scanner;
public class PrimeNumber {
public static void main(String[] args) {
Scanner sc = new Scanner(System.in);
System.out.println("Enter the Number: ");
int num= sc.nextInt();
boolean flag = false;
for(int i = 2; i <= num/2; ++i)
{
if(num % i == 0)
{
flag = true;
break;
}
}
if (!flag)
System.out.println(num + " Is A Prime Number");
else
System.out.println(num + " Is Not A Prime Number");
}
}
Enter the Number: 7 7 Is A Prime Number