Java 对 Guava TreeBasedTable 进行排序 [英] Java Sort a Guava TreeBasedTable

问题描述

我有一个来自 Guava (Gooogle Collections) 的 TreeBasedTable 对象.它的形式是TreeBasedTable.k1 和 k2 实现了 Comparable.现在，当我显示表格时，我希望用户能够以不同的方式对其进行排序以更改值的顺序.

I have a TreeBasedTable object from Guava (Gooogle Collections). It is in the form of TreeBasedTable<k1, k2, v>. k1 and k2 implement Comparable. Now when I display the table, I want the user to be able to sort it different ways to change the order of the values.

我尝试的方法是遍历表，并为每个值更改比较方法中使用的变量.问题是它通过循环一次，然后返回一个 NullPointerException，我想我已经缩小范围，尝试在迭代时更改顺序(新手错误，我知道).

The approach I tried was to iterate over the table, and for each value, change a variable that's used in the Compare method. The trouble is it gets through the loop once, and then returns a NullPointerException, which I think I've narrowed down to trying to change the order whilst iterating over it (rookie mistake, I know).

所以我想知道重新排序这张表的好方法是什么?

So I was wondering, what would be a good way to reorder this table?

推荐答案

如果你只是创建一个新的 TreeBasedTable，使用不同的比较器对象创建，然后通过 public putAll 方法将原始复制到其中会怎样?每个元素的 put 将花费 log(N)，所以总时间应该是 N log(n)，这大约是我期望重新排序花费的时间.

How about if you just create a new TreeBasedTable, created with a different comparator object, and then copy the original into it via public putAll method? The put for each element will take log(N), so total time should be N log(n), which is about the time I would expect for a re-sort to take.

这篇关于Java 对 Guava TreeBasedTable 进行排序的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！