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UnsupportedOperationException when trying to remove a list of items from another list

java,listiterator
I have coded below, i dint know what is wrong but validDatesIterator.remove() is giving me UnsupportedOperationException exception. Using java 1.6 List<Integer> validDates = Arrays.asList(26,27,28,1,2,3,4); List<Integer> daysToBeRemoved = Arrays.asList(1,2); Iterator<Integer> validDatesIterator = validDates.listIterator(); while(validDatesIterator.hasNext()) { Integer curValue = validDatesIterator.next(); for(Integer dayToRemove:daysToBeRemoved) { if(curValue.equals(dayToRemove)) { validDatesIterator.remove(); break; } } }...

Iterating twice over HashMap Java

java,iterator,hashmap,listiterator
I have a HashMap declared as static HashMap<String,ArrayList<Integer>> inverted_index = new HashMap<String,ArrayList<Integer>>(); I iterated over its keys as public static void printInvertedIndex() throws FileNotFoundException{ PrintWriter writer = new PrintWriter(new File("InvertedIndex.txt")); Iterator it = inverted_index.entrySet().iterator(); while (it.hasNext()) { Map.Entry pair = (Map.Entry)it.next(); writer.println(pair.getKey() + " " + pair.getValue()); it.remove(); } writer.close();...

Adding items to a HashMap while looping with Iterator

java,iterator,hashmap,listiterator
I have a program that loops through a HashMap using an Iterator, and inside the loop, I'm adding to the HashMap - which is causing a ConcurrentModificationException. I've seen that ListIterator has an add() function that handles this, but Iterator does not. The HashMap is set up like this -...

why java API prevents us to call add and remove together?

java,list,collections,listiterator
As per Java API- IllegalStateException - if neither next nor previous have been called, or remove or add have been called after the last call to next or previous remove()- Removes from the list the last element that was returned by next() or previous() (optional operation). This call can only...

Iterator for an array list of Class

java,collections,iterator,listiterator
Am New to Java so please bear with me if my question seems to be silly. I am learning collections,I have written a program which will store student names id and marks.I am storing all these in a Arraylist. Using for loop I am able to print the values in...

Python Linked List with Nodes. Iterable

python,linked-list,listiterator
I need some help writing an __iter__() method for my UnorderedList() class. I tried this: def __iter__(self): current = self while current != None: yield current But the while loop doesn't stop. Here is the rest of my classes and code: class Node: def __init__(self,initdata): self.data = initdata self.next =...

How to conditionally remove an element from a list using an iterator?

c++,linked-list,listiterator
Problem: I am writing a simple file manager application. In this program I have a "Directory" class: class Directory { public: Directory(string address, string directoryname) { this->path = address; this->name = directoryname; } string GetFullPath(){ return path == "/" ? path + name : path + "/" + name; }...

Is linkedList.listIterator(linkedList.size()) optimized?

java,linked-list,reverse,listiterator
I'm trying to create a reverse ListIterator for a LinkedList, and was going to just implement it as a wrapper to linkedList.listIterator(linkedList.size()) that swaps the next and previous operations, but then realized that if LinkedList#listIterator(int) is implemented to just traverse forwards to the position specified, using it to start at...

Removing an item from a list in Java

java,arrays,list,iterator,listiterator
I've scoured this site (as well as the web) and for some reason cannot find an answer that works. Either I get an index out of bounds error, or the next part of my code won't execute. All I am trying to do is remove a item from a list...