v What
us Prime Number
Different View of the Logic
Example-2:
Example-3:
Example-4:
§ If
a whole number greater than 1, is divisible by the 1 and itself then it is
known as Prime Number.
§ A
prime number is a number which is divisible by only two numbers: 1 and itself.
So, if any number is divisible by any other number, it is not a prime number.
Different View of the Logic
§ The
number cannot divisible by any number between 2 to n-1
Example-1:
import java.util.Scanner;
public class PrimeNumber {
static boolean
isPrime(int n) {
boolean flag = false;
if(n>1)
{
for(int i=2;i<=n-1;i++) {
//
condition for nonprime number
if(n%i==0) {
flag=true;
break;
}
}
}
if(!flag)
return true;
else
return false;
}
public static void
main(String[] args) {
// TODO
Auto-generated method stub
Scanner sc=new
Scanner(System.in);
System.out.println("Enter
number");
int num=sc.nextInt();
boolean res=isPrime(num);
if (res)
System.out.println(num + "
is a prime number.");
else
System.out.println(num + "
is not a prime number.");
}
}
Example-2:
§ The
number can’t divisible by any number between 2 to n/2.
import java.util.Scanner;
public class PrimeNumber {
static boolean
isPrime(int n) {
boolean flag = false;
int i=2;
while(i <=
n/2)
{
// condition for nonprime
number
if(n% i == 0)
{
flag = true;
break;
}
++i;
}
if (!flag)
return true;
else
return false;
}
public static void
main(String[] args) {
// TODO
Auto-generated method s*- nhgtub
Scanner sc=new
Scanner(System.in);
System.out.println("Enter number");
int num=sc.nextInt();
boolean res=isPrime(num);
if (res)
System.out.println(num + "
is a prime number.");
else
System.out.println(num + "
is not a prime number.");
}
}
Example-3:
§ The
number can’t divisible by any number between 2 to sqrt(n)
import java.util.Scanner;
public class PrimeNumber {
static boolean
isPrime(int n) {
boolean flag = false;
int i=2;
while(i <=
Math.sqrt(n))
{
// condition for nonprime
number
if(n% i == 0)
{
flag = true;
break;
}
++i;
}
if (!flag)
return true;
else
return false;
}
public static void
main(String[] args) {
// TODO
Auto-generated method stub
Scanner sc=new
Scanner(System.in);
System.out.println("Enter
number");
int num=sc.nextInt();
boolean res=isPrime(num);
if (res)
System.out.println(num + "
is a prime number.");
else
System.out.println(num + "
is not a prime number.");
}
}
Example-4:
§ A number which
having only two factors is known as prime number
for e.g.: -
3 having two
factor 1 ,3 so 3 is a prime number
6 having more than
two factor 1,2,3,6 so 6 is not a prime number.
import
java.util.Scanner;
public class
PrimeNumber {
static int factorCount(int n) {
int count=0;
for(int i=1;i<=n;i++) {
if(n%i==0)
count++;
}
return count;
}
static boolean isPrime(int n) {
int c=factorCount(n);
if(c==2)
return true;
else
return false;
}
public static void main(String[] args) {
// TODO
Auto-generated method stub
Scanner sc=new
Scanner(System.in);
System.out.println("Enter
number");
int n=sc.nextInt();
boolean res=isPrime(n);
if(res==true)
System.out.println(n+"
is a Prime Number!");
else
System.out.println(n+"
is not a Prime Number!");
}
}
