To write a java program that prompts the user for an integer and then prints out all prime numbers up to that integer.

 Prime Numbers

Aim:

To write a java program that prompts the user for an integer and then prints out all prime numbers up to that integer.

Description: 

A prime number is a positive integer that is exactly divisible only by 1 and itself. The first few prime numbers are: 2 3 5 7 11 13 17 23 29 31 37 … To do this; let us consider a number 13. The definition of prime number suggests that to determine whether or not 13 is prime, we need to divide it in turn by the set of numbers 2, 3, 4, 5 …12. If any of these numbers divide into 13 without remainder we will know it cannot be prime number.That is, we can test for mod operation with numbers, from 2 to n-1.

Program:
import java.io.*;
class Prime
{ public static void main(String args[])throws IOException
{ int i,j,a=0,n;
BufferedReader br= new BufferedReader(new InputStreamReader (
System.in) );
System.out.println("Enter range : " );
n = Integer.parseInt(br.readLine() );
for(i=2;i<=n;i++)
{
a=0;
for(j=2;j<i;j++)
{
if(i%j==0)
a=1;
}
if(a==0)
System.out.print(i + "\t");
}
}
}