计算质数(极速版)

计算1000000以内的质数只用了398毫秒,闪电一样的速度.

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long start = System.currentTimeMillis();

for (int i = 1; i < 100; i++) {
	double r = Math.sqrt(i);
	for (int j = 2; j < r; j++) {
		if(i % j == 0) {
			break;
		}else if( j > r )
		{
			System.out.println(i);
		}
	}
}

long end = System.currentTimeMillis();
System.out.println(end - start);