calendar.getInstance()或calendar.clone()

Question

我需要复制一个给定日期100次(我不能通过参考传递).我想知道下面哪两个是更好的选择

newTime=Calendar.getInstance().setTime(originalDate);

要么

newTime=originalDate.clone();

表演在这里是主要的.

谢谢.

Answer 1

我会用

newTime= (Calendar) originalDate.clone();

Answer 2

1. 我的直觉告诉我,clone()会更快.
2. 为什么不试试快速基准[*]？
3. date.getTime()如果您不必进行日历计算,请考虑仅使用长值.

[*]

private static final int N = 100000;

public static void main(final String[] args) throws Exception {

    final Date date = new Date();

    {
        final long start = System.currentTimeMillis();
        for (int i = 0; i < N; i ++) {
            final Date date2 = (Date) date.clone();
        }
        final long end = System.currentTimeMillis();
        System.out.println("Clone: " + (end - start) + " ms");
    }
    {
        final long start = System.currentTimeMillis();
        for (int i = 0; i < N; i ++) {
            final Calendar cal = Calendar.getInstance();
            cal.setTime(date);
            final Date date2 = cal.getTime();
        }
        final long end = System.currentTimeMillis();
        System.out.println("Caldendar.setTime: " + (end - start) + " ms");
    }
}

结果:

Clone: 13 ms
Caldendar.setTime: 317 ms

PS我不确定,如果你真的需要a Calendar或者a Date,那么随意修改测试......

(回应评论:为了提高测试准确性,您还可以单独运行测试,增加N的值,......)