collections

问题 Collections.sort(ar, new Comparator<Intervals>() { @Override public int compare(Intervals o1, Intervals o2) { return (Integer.valueOf(o1.getEnd())) .compareTo(Integer.valueOf(o2.getEnd())); } }); Hi all, I have the above code in java. Here, ar is a list and Intervals is a class with 2 integer variables : Start and End. I wanted to know what sorting algorithm is followed when we override the compare method of Comparator interface as above. I know, by default Collections.sort() and Arrays.sort(

问题 I have 3 MySql tables: Students , Classes and StudentsInClasses . The Entity Framework translates these into two entities Student and Class , each linking to the other with a many-to-many navigation property (e.g. Student.Classes ). But there is no StudentsInClasses entity, so what's the best way to call, using LINQ to Entities, the equivalent of SQL : SELECT StudentId, ClassId FROM StudentsInClasses; I'm looking for a HashSet (or equivalent) of { StudentId, ClassId } pairs so I can quickly

问题 I have a Flex question, which isn't as easy as it seems at first. At least I'm struggling since 1 week with it. I have prepared a test case and a screenshot. The question is: how do you merge data (coming repeatedly from server) into a filtered ArrayCollection? The screenshot: The TestCase.mxml (just place it into a Flash Builder 4.6 project): <?xml version="1.0" encoding="utf-8"?> <s:Application xmlns:fx="http://ns.adobe.com/mxml/2009" xmlns:s="library://ns.adobe.com/flex/spark"> <fx

问题 I have a form where users can modify a collection of objects using a DataGrid. When the form is opened I create a deep copy of the original collection and if the Cancel button is pressed I just discard that copy. The problem is that when the OK button is pressed I have to reconcile the changes which might be: Modified properties of existing objects New objects added to any place in the collection. Existing objects removed. Existing objects re-ordered. Since I need to keep the original

问题 With the snippet below I am, attempting to process a spreadsheet, with the twist of needing to exclude ad hoc columns. I know the crude way I am doing it, put the exceptions in an ArrayList and process the list on each and ever increment over the current row columns is perverse, but you know just get it done. However I am getting the titled error, which I believe should never happen. I am just looping through the ArrayList and comparing, not modifying anything. Where is the error? Is there a

问题 I have two lists generated with a FactoryBean and I would like to initialize a bean with the merged version of this two. Is there a way doing this? <bean id="listA" class="XFactoryBean" > ... </bean> <bean id="listB" class="YFactoryBean"> ... </bean> <bean > <property name="AwithB" ...> </bean> There is a solution that works with static lists (http://vikdor.blogspot.hu/2012/10/using-collection-merging-in-spring-to.html), but does not work with those generated lists. 回答1: Java @Configuration

问题 private List<String> subList; private List<List<String>> records = new ArrayList<List<String>>(); for(....){ subList = new ArrayList<String>(); ...populate.. records.add(subList); } For example, subList has three Strings - a, b, and c. I want to sort the records by the value of b in subList. records at 0 has a list of "10", "20", "30" records at 1 has a list of "10", "05", "30" records at 2 has a list of "10", "35", "30" After the sort, the order of records should be - records at 0 = records

问题 My Problem I have the following spec: Write a function that given a list of non negative integers, arranges them such that they form the largest possible number. For example, given [50, 2, 1, 9], the largest formed number is 95021. My Results I have taken a stab at a solution to the problem, but it fails. For example, given the input [90,91,89,999] the result of this code is [909199989], but it should have been [999919089]. A Description of My Algorithm In simple words it is a reverse of

问题 In Java 9 we have convenience factory methods to create and instantiate immutable List, Set and Map. However, it is unclear about the specific type of the returned object. For ex: List list = List.of("item1", "item2", "item3"); In this case which type of list is actually returned? Is it an ArrayList or a LinkedList or some other type of List? The API documentation just mentions this line, without explicitly mentioning that its a LinkedList: The order of elements in the list is the same as the

问题 This is a two part question: Does HashSet implement some hidden ordering mechanic or it just, to quote the documentation: It makes no guarantees as to the iteration order of the set; in particular, it does not guarantee that the order will remain constant over time. tells me that the order MIGHT change sometimes in the future and/or depending on memory usage? Why am I getting completely different 'ordering' (dare I say) when I switch between JDKs? Take this example: for (int i = 0; i < 1000;