**Objectives :**

- Write a Java program to find prime number upto N number
- Write a Java program to print prime number upto N number
- Write a Java program to find prime number upto N number using Command Line Arguments
- Write a Java Program to find prime number upto N number via Command Line Arguments
- Write a Java program to find prime number upto N number using Scanner class

**Java Program / Code :**

**Method 1 : Java Program to find Prime Number upto N number using Scanner class**

[sourcecode lang=”Java”]

import java.util.Scanner;

class PrimeNumber

{

public static void main(String[] args)

{

int n,p;

Scanner s=new Scanner(System.in);

System.out.println(“Enter number : ”);

n=s.nextInt();

for(int i=2;i<n;i++)

{

p=0;

for(int j=2;j<i;j++)

{

if(i%j==0)

p=1;

}

if(p==0){

System.out.println(i);

}

}

}

}

[/sourcecode]

**Method 2 : Java Program to find Prime Number upto N number using Scanner class and writing function to find prime number**

Method isPrime() for checking if a number is prime or not

[sourcecode lang=”java”]

public class PrimeNumber{

public boolean isPrime(int num) {

if ( num < 2 ){

return false;

}

for (int i = 2; i <= Math.sqrt(num); i++) {

if ( num % i == 0 ) {

return false;

}

}

return true;

}

}

// Mock Test Class to test above code

import java.util.Scanner;

public class Demo

{

public static void main(String[] args)

{

Scanner scanner = new Scanner(System.in);

System.out.println("Please enter a number: ");

int num = scanner.nextInt();

if ( num < 2 ) {

System.out.println("\n There are no Prime Numbers available");

System.exit(0);

}

System.out.println("\n Prime Numbers from 1 to "+ num);

PrimeNumber primeNum = new PrimeNumber();

for (int i = 3; i <= num; i++) {

if ( primeNum.isPrime(i) ) {

System.out.print(", " + i);

}

}

}

}

[/sourcecode]

**Method 3 : Java Program to find Prime Number upto N number using Command line input**

[sourcecode lang=”Java”]

class PrimeNumber

{

public static void main(String[] args)

{

int n,p;

n=Integer.parseint(args[0]);

for(int i=2;i<n;i++)

{

p=0;

for(int j=2;j<i;j++)

{

if(i%j==0)

p=1;

}

if(p==0){

System.out.println(i);

}

}

}

}

[/sourcecode]

Steps to run above program via command line :

- Compilation : C:\JavaPrograms>javac PrimeNumber.java
- Interpretation : C:\JavaPrograms>java PrimeNumber 20

Output :

2

3

5

7

11

13

17

19

for(int i=2 ; i & lt ; n ; i++)

{

p=0;

for(int j=2;j<i;j++)

what is this lt here?