1-n 以内的素数

static void ListPrime(int n) {
/**
* false为质数,true为合数
*/
boolean[] primeList = new boolean[n + 1];

for (int i = 2; i <= n; i++) {
if (!primeList[i]) {
int j = i * i;
if (j > n)
break;
if (i > 2) {
while (j <= n) {
primeList[j] = true;
j = j + i + i;
}
} else {
while (j <= n) {
primeList[j] = true;
j = j + i;
}
}
}
}
List<Integer> ret = new ArrayList<Integer>(10000);
ret.add(2);
for (int i = 3; i <= n;) {
if (!primeList[i]) {
//System.out.print(i + " ");
ret.add(i);
}
i += 2;
}
System.out.println(ret.size());
}