list对象数组根据对象某个属性去重或者排序

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/**
		 * 按照List中的某个String类型的属性进行排序
		 * 
		 * @param list
		 */

		Collections.sort(classList, new Comparator() {
			@Override
			public int compare(Object o1, Object o2) {
				ExamineeClass e1 = (ExamineeClass) o1;
				ExamineeClass e2 = (ExamineeClass) o2;
				return e1.getClassName().compareTo(e2.getClassName());
			}
		});
		
		
		按照List中的某个String类型的属性进行去重
List<User> userListNoDupAndSort = removeDuplicateUser(userList);
		 private static ArrayList<User> removeDuplicateUser(List<User> users) {
        Set<User> set = new TreeSet<User>(new Comparator<User>() {
            @Override
            public int compare(User o1, User o2) {
                //字符串,则按照asicc码升序排列
                return o1.getUserId().compareTo(o2.getUserId());
            }
        });
        set.addAll(users);
        return new ArrayList<User>(set);
    }
	
	
Java  8 去重
	users.stream().collect(Collectors.collectingAndThen(Collectors.toCollection(()->newTreeSet<>(Comparator.comparing(User::getUserId))), ArrayList::new))