java - 查找 ArrayList 的 ArrayList 的最大值，key = length

Question

我有一个包含 ArrayList 的 ArrayList

ArrayList<ArrayList<String>> allChains = new ArrayList<ArrayList<String>>();

我需要找出其中的最大值，key = length。在 python 中，我可以使用下面的方法做同样的事情，如何在 Java 中做同样的事情。

>>> l = [ ["apple", "b", "c"], ["a"], ["a","b","c","d"]]
>>> max(l, key=len)
['a', 'b', 'c', 'd']

Answer 1

您可以使用 Java 8 流:

ArrayList<ArrayList<String>> allChains = new ArrayList<>();
allChains.add (new ArrayList<String>(Arrays.asList ("apple", "b", "c")));
allChains.add (new ArrayList<String>(Arrays.asList ("a")));
allChains.add (new ArrayList<String>(Arrays.asList ("a","b","c","d")));

ArrayList<String> longest = allChains.stream()
                                     .max(Comparator.comparingInt(ArrayList::size))
                                     .get();

System.out.println (longest);

输出:

[a, b, c, d]