方法1:
import java.util.Date;
import java.util.HashSet;
import java.util.Set;
import java.util.TreeSet;
/**
* @author hanchen
* @create 2019-03-20 15:58
*/
public class PrimeNUm {
public static void main(String[] args) {
long k = new Date().getTime();
//Set set=new TreeSet();
for (int n = 1; n <= 1000; n += 2) {
int i;
for ( i = 2; i <n; i++) {
if (n % i == 0) break;
}
if(i==n)
System.out.println(n);
}
System.out.println(new Date().getTime() - k);
}
}