[Java知识库]Java - 测试方法运行时长 System.currentTimeMillis()

public class Timer {
    public static void main(String[] args) {
        int n = 100000;
        long begin = System.currentTimeMillis();
        int res = sum(n);
        long end = System.currentTimeMillis();
        System.out.println(n + "以内数字累加和: " + res);
        System.out.println("总耗时: " + (end - begin) + "毫秒");
    }

    public static int sum(int n) {  //计算累加和
        int sum = 0;
        for (int i = 0; i <= n; i++) {
            sum += i;
        }
        return sum;
    }
}

结果输出：

100000以内数字累加和: 705082704
总耗时: 2毫秒