Here’s a problem that you some times come across in problem sets and job interviews:

*Q. Write a program to generate all the prime numbers up to N.*

The simplest algorithm I can think of is the Sieve of Eratosthenes.

Here’s my attempt:

```
public class PrimeSieve {
public static void main(String[] args) {
int N = Integer.parseInt(args[0]);
boolean[] isPrime = new boolean[N+1];
Arrays.fill(isPrime, true);
int max = (int)Math.sqrt(N);
for (int i=2; i<=max; i++) {
if (isPrime[i]) {
// Remove all of the multiples of i
for (int j=2; i*j<=N; j++) {
isPrime[i*j] = false;
}
}
}
// List the primes
for (int k=2; k<=N; k++) {
if (isPrime[k]) System.out.print(k+" ");
}
}
}
```

That's all. You can leave now.