A number that has only two factors 1 and by itself or we can say a number that is divisible by 1 and by itself. Say 5, it is divisible by 1, and by itself, that is 5 is called a Prime number.
Prime number in Java
In the
following Java code, we have to check a number is prime or not by dividing the number by 1
to the number itself. If the counter is equal to 2 then the entered number is prime
otherwise not prime.
import
java.util.*;
public
class PrimeNumberTwofactor
{
public static void main(String args[])
{
Scanner sc=new Scanner(System.in);
int number, i, counter=0;
System.out.println("Enter a
number:");
number=sc.nextInt();
for(i=1; i<=number; i++)
{
if(number % i == 0)
{
counter++;
}
}
if(counter == 2)
{
System.out.println("Prime
Number");
}
else
{
System.out.println("Not a
Prime Number");
}
}
}
Another Version of Java Prime Number
package Javaclass;
import java.util.Scanner;
public class PrimeNumber {
public static void main(String[] args) {
int num, i, flag=1;
Scanner sc=new Scanner(System.in);
System.out.println("Enter a number");
num=sc.nextInt();
for(i=2; i<num; i++)
{
if(num % i == 0)
{
flag=0;
break;
}
}
if(flag==1) {
System.out.println("Prime number");
}
else
{
System.out.println("Not Prime number");
}
}
}
Prime number in Java with the method
In the
following code, the prime will be checked with a prime() method. One number is
passed through the prime(number) in the main() method by the user and after
checking the number is divisible by other than 1 and the number itself. If
divisible it will return 0 other 1.
import
java.util.*;
public
class PrimeNumber
{
int i, num, flag;
int prime(int n)
{
flag = 1;
num=n;
for(i=2; i<num; i++)
{
if(num % i == 0)
{
flag = 0;
break;
}
}
return flag; // flag variable return 1
or 0
}
public static void main(String args[])
{
Scanner sc=new Scanner(System.in);
int number;
int f;
PrimeNumber ob = new PrimeNumber(); //
object of the class
System.out.println("Enter a
number:");
number=sc.nextInt();
f=ob.prime(number);
if(f == 1) // check the flag variable 1 / 0
System.out.println("Prime
number");
else
System.out.println("Not a
Prime number");
}
}
Prime number in Java with a method with boolean return
In the
following piece of code, the prime will be checked with a prime () method and return a value boolean. One number is passed through the prime (number) in the main() method
by the user and after checking the number is divisible by other than 1 and the
number itself. If divisible it will return false other true.
import java.util.*;
public
class PrimeNumberCheck
{
int i, num; // instance varaible
boolean flag; // flag variable (instance variable)
boolean prime(int n)
{
flag = true;
num = n;
for(i=2; i<num; i++)
{
if(num % i == 0)
{
flag = false;
break;
}
}
return flag;
}
public static void main(String args[])
{
Scanner sc=new Scanner(System.in);
int number;
boolean f1; // boolean variable
// object of class PrimeNumberCheck
PrimeNumberCheck ob=new
PrimeNumberCheck();
System.out.println("Enter two
number:");
number = sc.nextInt();
f1 = ob.prime(number);
if(f1 == true ) // if 1 then prime or
not prime
System.out.println("Prime
number");
else
System.out.println("Not a
Prime number");
}
}
More Java program
