在Java中，如何从当天升序到最近7天? [英] how can i get last 7 days from current day in ascending order in java?

问题描述

我正在使用以下代码来获取最近7天:

I am using following code to get the last 7 days:

SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd ");
Calendar cal = Calendar.getInstance();
Date date = cal.getTime();
String[] days = new String[6];
days[0] = sdf.format(date);

for(int i = 1; i < 6; i++){
    cal.add(Calendar.DAY_OF_MONTH, -1);
    date = cal.getTime();
    days[i] = sdf.format(date);
}

for(String x: days){
    System.out.println(x);
}

这给出了以下输出:

2016-04-14
2016-04-13
2016-04-12
2016-04-11
2016-04-10
2016-04-09

但是我想要这个:

2016-04-09
2016-04-10
2016-04-11
2016-04-12
2016-04-13
2016-04-14

如果我在代码下方使用以下行，它将给我正确的顺序:

If I use the following line below the code it will give me the correct order:

List<String> list = Arrays.asList(days);
Collections.reverse(list);
days = (String[]) list.toArray();

for(String x: days){
    System.out.println(x);
}

但是还有其他方法可以使最后7天一次升序吗?

But is there any other way to get the last 7 days in ascending order in one shot?

推荐答案

我会稍微简化您的方法，如果您想要此输出，则无需创建 String [] 数组，每个循环两次，您可以使用一个 for-loop ，一个 Calendar 和 SimpleDateFormat

I would simplify your method a bit, if you want this output you don't need to create an String[] array, either loop twice, you can achieve same with a single for-loop, one Calendar and the SimpleDateFormat

SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd ");
Calendar cal = Calendar.getInstance();
// get starting date
cal.add(Calendar.DAY_OF_YEAR, -6);

// loop adding one day in each iteration
for(int i = 0; i< 6; i++){
    cal.add(Calendar.DAY_OF_YEAR, 1);
    System.out.println(sdf.format(cal.getTime()));
}

输出:

2016-04-09 
2016-04-10 
2016-04-11 
2016-04-12 
2016-04-13 
2016-04-14 

正在运行的IDEONE演示

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