What is a prime number in Java?
A prime number in java is a number that is greater than 1 and divided by 1 or itself only. or we can say that a prime number can be divided by 1 or itself.
A number greater than 1 that is not prime is called a composite number.
for example:- 7 is a prime number because 7*1=7 or 1*7=7.
2=1,2 it is prime
3=1,2 it is prime
4=1,2,4 it is not prime
5=1,5 it is prime
6=1,2,3,6 it is not prime
Algorithm of prime number
simple steps of prime number:-
START Step 1 → Take integer variable num Step 2 → Divide the variable num with (num-1 to 2) Step 3 → If num is divisible by any value (num-1 to 2) not prime Step 4 → Else it is prime STOP
Prime Number in java using a for loop
public class Main {
public static void main(String[] args) {
int a = 11;
boolean flag = false;
for (int loop = 2; loop <= a / 2; ++i) {
// condition for nonprime number
if (a % loop == 0) {
flag = true;
break;
}
}
if (!flag)
System.out.println(a + " is a prime number.");
else
System.out.println(a + " is not a prime number.");
}
}
Output
11 is a prime number
Prime Number in java using a while loop
public class Main {
public static void main(String[] args) {
int a = 11, loop = 2;
boolean flag = false;
while (loop <= a / 2) {
// condition for nonprime number
if (a % loop == 0) {
flag = true;
break;
}
++loop;
}
if (!flag)
System.out.println(a + " is a prime number.");
else
System.out.println(a + " is not a prime number.");
}
}
Output
11 is a prime number
Prime Number in Java using Scanner
import java.util.Scanner;
import java.util.Scanner;
public class Prime {
public static void main(String[] args) {
Scanner s = new Scanner(System.in);
System.out.print(“Enter a number : “);
int num = s.nextInt();
if (isprime(num)) {
System.out.println(“it is a prime number”);
}
else {
System.out.println(” it is not a prime number”);
}
}
public static boolean isprime(int num) {
if (num <= 1) {
return false;
}
for (int loop = 2; loop < Math.sqrt(num); loop++) {
if (num % loop == 0) {
return false;
}
}
return true;
}
}
Output
Enter the number : 3 it is a prime number