100以内质数

for(int i = 1; i < 100; i++)
{
int j = 2;
for( ; j < i; j++)
{
if(i%j == 0)
{
break;
}
}
if( i == 1 || i == j)
{
System.out.println(i);
}
}

1. ArrayList<Integer> al = new ArrayList<Integer>();
2. al.add(2);
3.System.out.println(2);
4. for (int i = 2; i <= 50000; i++) {
5. boolean ok = true;
6. for (int t : al) { //用已有质数集作判断,减少比较次数
7. if (i % t == 0) {
8. ok = false;
9. break;
10. }
11. if (t > i / 2) {
12. break;
13. }
14. }
15. if (ok) {
16. System.out.println(i);
17. al.add(i);
18. }
19. }


long start3 = System.currentTimeMillis();
3. int[] temp = { 2, 3, 5, 7 };
4. label2: for (int i = 2; i <= 100000; i++) {
5. for (int j = 0; j < temp.length; j++) {
6. if (i % temp[j] == 0)
7. continue label2;
8. }
9. // System.out.print(i + " ");
10. }
11. long end3 = System.currentTimeMillis();
12. System.out.println("Time is " + (end3 - start3) + " milliseconds");// 15 milliseconds