java8排序

1. 一：對整數進行排序

2. List<Integer> numbers =Arrays.asList(6,2,1,4,9);

3. System.out.println(numbers);//[6, 2, 1, 4, 9]

4. numbers.sort(Comparator.naturalOrder());

5. System.out.println(numbers);//[1, 2, 4, 6, 9]

6. 二、按字符串字段對列表進行排序

7. 1. List<Movie> movies =Arrays.asList(

   2. newMovie("Lord of the rings"),

   3. newMovie("Back to the future"),

   4. newMovie("Carlito's way"),

   5. newMovie("Pulp fiction"));

   6. movies.sort(Comparator.comparing(Movie::getTitle));

   7. movies.forEach(System.out::println);

   8. 提取的類型是String,而String實現了 Comparable接口,所以list能正確排序。

   9. 三、按double字段排序列表

   10. List<Movie> movies =Arrays.asList(

   11. newMovie("Lord of the rings",8.8),

   12. newMovie("Back to the future",8.5),

   13. newMovie("Carlito's way",7.9),

   14. newMovie("Pulp fiction",8.9));

   15. movies.sort(Comparator.comparingDouble(Movie::getRating)

   16. .reversed());

   17. movies.forEach(System.out::println);

   18. 我們使用反轉函數( reversed)來反轉默認從低到高的自然排序， Comparator.comparingDouble() 底層使用 Double.compare()實現。如果需要比較 int或 long，可以分別使用 comparisonInt()和 comparisonLong()。
   19. 四、使用自定義比較器多列表進行排序

   20. 1. List<Movie> movies =Arrays.asList(

       2. newMovie("Lord of the rings",8.8,true),

       3. newMovie("Back to the future",8.5,false),

       4. newMovie("Carlito's way",7.9,true),

       5. newMovie("Pulp fiction",8.9,false));

       6. movies.sort(newComparator<Movie>(){

       7. @Override

       8. publicint compare(Movie m1,Movie m2){

       9. if(m1.getStarred()== m2.getStarred()){

       10. return0;

       11. }

       12. return m1.getStarred()?-1:1;

       13. }

       14. });

       15. 我們可以使用 lambda表達式而不是匿名類( Anonymousclass)，如下所示:

       16. movies.forEach(System.out::println);

       17. 1. movies.sort((m1, m2)->{

           2. if(m1.getStarred()== m2.getStarred()){

           3. return0;

           4. }

           5. return m1.getStarred()?-1:1;

           6. });

           7. 也可以使用 Comparator.comparing():

           8. 1. movies.sort(Comparator.comparing(Movie::getStarred,(star1, star2)->{

              2. if(star1 == star2){

              3. return0;

              4. }

              5. return star1 ?-1:1;

              6. }));

1. List<Integer> numbers =Arrays.asList(6,2,1,4,9);

2. System.out.println(numbers);//[6, 2, 1, 4, 9]

3. numbers.sort(Comparator.naturalOrder());

4. System.out.println(numbers);//[1, 2, 4, 6, 9]

 

 

 

原文鏈接：https://dzone.com/articles/java-8-comparator-how-to-sort-a-list

 

作者： Mario Pio Gioiosa

 

譯者：Steephan