使用Array.sort和Lambda表达式对对象进行降序排序

Question

I want to sort a collection of objects in descending order.

Below code is working to sort the itemDetails object in ascending order.

Arrays.sort(itemDetails, (a, b) -> 
    String.valueOf(a.getAvailableQuantity())
          .compareTo(String.valueOf(b.getAvailableQuantity())));

But I wanted the output in descending order.

Answer 1

Switch to (b, a) :

Arrays.sort(itemDetails, (b, a) ->
    String.valueOf(a.getAvailableQuantity())
          .compareTo(String.valueOf(b.getAvailableQuantity())));

Actually change names to meaningful so sorting logic will be understandable

Answer 2

Use Comparator.comparing (to avoid having to repeat the String.valueOf and getAvailableQuantity ) and Comparator.reversed() (to clearly convey the fact that you are reversing the sort order):

Arrays.sort(
    itemDetails,
    Comparator.comparing((ItemDetails a) -> String.valueOf(a.getAvailableQuantity())).reversed());

where ItemDetails is the name of the element type of the array (or some supertype which also has the getAvailableQuantity method).

Answer 3

加减号：

Arrays.sort(itemDetails, (a, b) -> -String.valueOf(a.getAvailableQuantity()).compareTo(String.valueOf(b.getAvailableQuantity())));