排序Bean的Arraylist的Arraylist [英] Sorting Arraylist of Arraylist of Bean

问题描述

我有一个 ArrayList 的 ArrayList 的Bean和我需要排序这个 ArrayList

I have an ArrayList of ArrayList of Bean and I need to sort this ArrayList according to the date variable in Bean.

ArrayList<ArrayList<DriverLogDatePair>> driverLogList

并且 DriverLogDatePair code> DateTime date ，它还有一个 compareTo 方法。

And DriverLogDatePair bean have a variable DateTime date, it also has a compareTo method.

public int compareTo(DriverLogDatePair o) {
    return date.compareTo(o.date);
}

但我不能排序 driverLogList 。

But I am not able to sort driverLogList.

推荐答案

您必须填写此代码：

ArrayList<ArrayList<DriverLogDatePair>> driverLogList = new ArrayList<>();
Collections.sort( driverLogList, new Comparator<ArrayList<DriverLogDatePair>>(){
   @Override public int compare(
      ArrayList<DriverLogDatePair> left,
      ArrayList<DriverLogDatePair> right )
   {
      return 0;
   }});

因为第一个数组包含一个包含Comparable的数组。
您提供的比较器是为DriverLogDatePair而不是ArrayList< DriverLogDatePair>

Because the first array contains an array which contains a Comparable. The comparator you provide is for DriverLogDatePair not for ArrayList< DriverLogDatePair >

（...在此帖子的评论...）

(... After comments of this post... )

完成比较我建议：

int size = left.size();
int diff = size - right.size();
if( diff != 0 ) return diff;
for( int i = 0; i < size; ++i ) {
   diff = left.get( i ).compareTo( right.get(i) );
   if( diff != 0 ) return diff;
}

但我不知道这个比较的真正含义。
这是一个语义问题，这是真的你想要什么？

But I have no idea of the true meaning of this comparison. It's a semantic problem, is this really what you want?

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