Sorting List of Arrays by different elements using Java 8 lambdas

Question

如果我有一个List<String[]> ，其中每个String[]如下所示：{FirstName，LastName，Income，City}我将如何使用Java 8 lambdas按列表对某个值进行排序，例如收入或名字？

Answer 1

Here's a couple examples. Replace x in the first two examples below with the index of the field you'd like to use for sorting.

Collections.sort(personList, (p1, p2) -> p1[x].compareTo(p2[x]));

or

personList.sort((p1, p2) -> p1[x].compareTo(p2[x]);

Also, I agree with @Robin Topper's comment. If lambdas are required (and you wanted to sort by first name), you could use:

Collections.sort(personList, (p1, p2) -> p1.getFirstName().compareTo(p2.getFirstName()));

or

personList.sort((p1, p2) -> p1.getFirstName().compareTo(p2.getFirstName()));

Also consider using the comparable implementation from Robin's comment and a data-structure allowing sorting.

Answer 2

If you can rely on the order in this array, then as simple as:

List<String[]> list = Arrays.asList(new String[] { "eugene", "test", "300", "LA" }, 
                              new String[] { "hunter", "test2", "25", "CA" });

 List<String[]> sorted = list.stream()
            .sorted(Comparator.comparingLong(s -> Long.parseLong(s[2])))
            .collect(Collectors.toList());

    sorted.forEach(s -> System.out.println(Arrays.toString(s)));

But the general advice to create an Object from those fields is much better.