concurrentmodification

问题 I have the following code public void start(Stage primaryStage) { BorderPane border_pane = new BorderPane(); TreeView tree = addTreeView(); //TreeView on the LEFT border_pane.setLeft(tree); /* more stuff added to the border_pane here... */ Scene scene = new Scene(border_pane, 900, 700); scene.setFill(Color.GHOSTWHITE); primaryStage.setTitle("PlugControl v0.1e"); primaryStage.setScene(scene); primaryStage.show(); } public static void main(String[] args) { launch(args); } With addTreeView being

问题 I am trying to implement merge sort in java, but this causes a ConcurrentModificationException in the line while(ai<la.size()&&bi<lb.size()){ . I have seen a lot of answers on Stack about this but they all relate to removing items from a list, but I am not doing that. What is causing this exception, and how can I fix this? public static <Elem extends Comparable<Elem>> void mergesort(List<Elem> list) { if(list.size()>1){ int hf = list.size()/2; List<Elem> la = list.subList(0, hf-1); List<Elem>

问题 Consider the following scenario Suppose there are three fields in a database table ------------------------------------------ PrmiaryKey | Column A | Column B ----------------------------------------- I need to enforce that for values in Column B should have unique values for Column A Example Col B Col A 12 13 (OK) 14 15 (OK) 15 16 (OK) 12 13 (OK) 15 16 (OK) 14 17 (not OK) Since value 14 previously have value 15 under Column B. So it should not have a different value than 15. I need to

问题 I am taking the insurance details from user and saving them in a hashmap. And I have button called SAVE. So only, when user clicks on this button all insurances should save in Database So I am taking a random generated id as reference until I save the details in Database After saving in database, I need to update this hashmap with key as autogenerated id public void saveInformationInDatabase(int patientId) { // getAllInsurances returns HashMapn<Integer, HashMap<Integer, InsuranceInformation>>

问题 I've copied an ArrayList over as so: MyList2 = MyList1; In an attempt to load MyList2's objects with the ones which MyList1 has. Now as I iterate through MyList2, I it.remove() some objects, but this is causing a concurrent modification exception elsewhere on the parent iteration through MyList1. I think when i it.remove() it's actually removing it from the original ArrayList as well, how do remove it only from MyList2? Thanks. 回答1: Your problem there is that you haven´t created a copy of the

问题 I am getting the below error while using map and performing some remove.How to avoid this ? Caused by: java.util.ConcurrentModificationException at java.util.HashMap$HashIterator.nextEntry(HashMap.java:793) at java.util.HashMap$EntryIterator.next(HashMap.java:834) at java.util.HashMap$EntryIterator.next(HashMap.java:832) Map<FormField, Object> ItemMap = domainItem.getValues(); for (Map.Entry<FormField, Object> ValMap : ItemMap.entrySet()) { List<Field> groupIdList = Mapper.getGroupId

问题 I know what a ConcurrentModificationException is. I had them before, I solved them before and I can get away with a Iterator. However, In this case I don't understand why it's being thrown. public boolean pointOnEdgeBlob(int x, int y, float edgeHitEpsilon) { init(); for (int i = 0; i < nOfBlobs; i++) { Blob b = blobs.get(i); // >>>>>>>>>>>>>>>>>>>>> here it calls the method where it goes wrong if (b.edgeHit(x, y, edgeHitEpsilon)) return true; } return false; } Here is the edgeHit method that

问题 I saw a blog a while back that said if you're having trouble with concurrentmodificationexception , convert the arraylist to a regular array[] and you'll be fine. It didn't explain it though. Why is this? 回答1: The iterators returned by this class's iterator and listIterator methods are fail-fast: if the list is structurally modified at any time after the iterator is created, in any way except through the iterator's own remove or add methods, the iterator will throw a

问题 I'm using an iterator to remove a projectile from a list if it goes out of the border of my JPanel. Before using the iterator it would not work, but with the iterator it works so long as I put the method into a try-catch for a ConcurrentModificationException . The code now works, and successfully removes the projectile from the list, but about 30% of the time, the catch hits and causes a stutter in my program. I don't know why it only catches sporadically, but in the limited time my professor

问题 I'm trying to get a List it's size but when doing this I'm getting a ConcurrentModificationException on the size() method. This is weird because I'm not trying to modify the list while iterating over it. Here's some of my code that might have caused it but I can't see the problem with it. The main method: private void setupCharacterGrid() { currentCharacters.add(0, new Character("add", "add")); if (currentCharacters.size() < 9) { sub(0, currentCharacters.size(), currentCharacters.size()); }