使用LinkedHashSet去重

  1. public class RemoveDuplicateExample {
  2.     public static void main(String[] args) {
  3.         //使用LinkedHashSet去重
  4.         ArrayList<Integer> numbersList = new ArrayList<Integer>(Arrays.asList(1, 1, 2, 3, 3, 3, 4, 5, 6, 6, 6, 7, 8));
  5.         List<Integer> result = new ArrayList<Integer>(numbersList.size());
  6.         LinkedHashSet<Integer> hashSet = new LinkedHashSet<>(numbersList);
  7.         ArrayList<Integer> listWithoutDuplicates = new ArrayList<>(hashSet);
  8.         System.out.println(listWithoutDuplicates);
  9.     }
  10. }

使用HashSet去重

  1. public class RemoveDuplicateExample {
  2.     public static void main(String[] args) {
  3.         //使用HashSet去重
  4.         //方式一:
  5.         ArrayList<Integer> numbersList = new ArrayList<Integer>(Arrays.asList(1, 1, 2, 3, 3, 3, 4, 5, 6, 6, 6, 7, 8));
  6.         HashSet h = new HashSet(numbersList);
  7.         numbersList.clear();
  8.         numbersList.addAll(h);
  9.         System.out.println(numbersList);
  11.         //方式二:
  12.         HashSet<Integer> set = new HashSet<Integer>(numbersList.size());
  13.         List<Integer> result = new ArrayList<Integer>(numbersList.size());
  14.         for (Integer integer : numbersList) {
  15.             if (set.add(integer)) {
  16.                 result.add(integer);
  17.             }
  18.         }
  19.         numbersList.clear();
  20.         numbersList.addAll(result);
  21.         System.out.println(numbersList);
  22.     }
  23. }

使用Stream流去重

  1. public class RemoveDuplicateExample {
  2.     public static void main(String[] args) {
  3.         //使用Stream去重
  4.         ArrayList<Integer> numbersList = new ArrayList<Integer>(Arrays.asList(1, 1, 2, 3, 3, 3, 4, 5, 6, 6, 6, 7, 8));
  5.         List<Integer> listWithoutDuplicates = numbersList.stream().distinct().collect(Collectors.toList());
  6.         System.out.println(listWithoutDuplicates);
  7.     }
  8. }

使用List的contains方法去重

  1. public class RemoveDuplicateExample {
  2.     public static void main(String[] args) {
  3.         //使用contains方法去重
  4.         ArrayList<Integer> numbersList = new ArrayList<Integer>(Arrays.asList(1, 1, 2, 3, 3, 3, 4, 5, 6, 6, 6, 7, 8));
  5.         List<Integer> result = new ArrayList<Integer>(numbersList.size());
  6.         for (Integer integer : numbersList) {
  7.             if (!result.contains(integer)) {
  8.                 result.add(integer);
  9.             }
  10.         }
  11.         numbersList.clear();
  12.         numbersList.addAll(result);
  13.         System.out.println(numbersList);
  14.     }
  15. }

使用双重for去重

  1. public class RemoveDuplicateExample {
  2.     public static void main(String[] args) {
  3.         //使用双重for去重
  4.         ArrayList<Integer> numbersList = new ArrayList<Integer>(Arrays.asList(1, 1, 2, 3, 3, 3, 4, 5, 6, 6, 6, 7, 8));
  5.         for (int i = 0; i < numbersList.size(); i++) {
  6.             for (int j = 0; j < numbersList.size(); j++) {
  7.                 if(i!=j&&numbersList.get(i)==numbersList.get(j)) {
  8.                     numbersList.remove(numbersList.get(j));
  9.                 }
  10.             }
  11.         }
  12.         System.out.println(numbersList);
  13.     }
  14. }