concurrentmodification

问题 If I spawn 2 threads on a single core PC does it ever access for example an ArrayList in the same time so it will throw ConcurrentModificationException ? My gut tells me although there are 2 threads, they cannot achieve true parallelism because there is a single core and what it can do mostly is to jump from one thread to another but without executing an instruction such as arrayList.add(element) in the same time. 回答1: TL;DR: Yes List<String> myList = new ArrayList<String>(Arrays.asList("My

问题 If I spawn 2 threads on a single core PC does it ever access for example an ArrayList in the same time so it will throw ConcurrentModificationException ? My gut tells me although there are 2 threads, they cannot achieve true parallelism because there is a single core and what it can do mostly is to jump from one thread to another but without executing an instruction such as arrayList.add(element) in the same time. 回答1: TL;DR: Yes List<String> myList = new ArrayList<String>(Arrays.asList("My

问题 If I spawn 2 threads on a single core PC does it ever access for example an ArrayList in the same time so it will throw ConcurrentModificationException ? My gut tells me although there are 2 threads, they cannot achieve true parallelism because there is a single core and what it can do mostly is to jump from one thread to another but without executing an instruction such as arrayList.add(element) in the same time. 回答1: TL;DR: Yes List<String> myList = new ArrayList<String>(Arrays.asList("My

问题 If I spawn 2 threads on a single core PC does it ever access for example an ArrayList in the same time so it will throw ConcurrentModificationException ? My gut tells me although there are 2 threads, they cannot achieve true parallelism because there is a single core and what it can do mostly is to jump from one thread to another but without executing an instruction such as arrayList.add(element) in the same time. 回答1: TL;DR: Yes List<String> myList = new ArrayList<String>(Arrays.asList("My

问题 I have implemented Resteasy service which is working under Apache Tomcat. It works fine, but sometimes, when sending request to service, very rarely I receive such crazy error: java.util.ConcurrentModificationException at java.util.ArrayList$Itr.checkForComodification(Unknown Source) at java.util.ArrayList$Itr.next(Unknown Source) at com.sun.xml.bind.v2.runtime.reflect.Lister$CollectionLister$1.next(Lister.java:288) at com.sun.xml.bind.v2.runtime.property.ArrayElementProperty

问题 I would like to use ConcurrentHashMap to let one thread delete some items from the map periodically and other threads to put and get items from the map at the same time. I'm using map.entrySet().removeIf(lambda) in the removing thread. I'm wondering what assumptions I can make about its behavior. I can see that removeIf method uses iterator to go through elements in the map, check the given condition and then remove them if needed using iterator.remove() . Documentation gives some info about

问题 Is there any way I can modify the HashMap values of a particular key while iterating over it? A sample program is given below: public static void main(String[] args) { HashMap<Integer,ArrayList<String>> hm = new HashMap<Integer, ArrayList<String>>(); ArrayList<String> ar = new ArrayList<String>(); for(int i=0;i<50;i++){ ar.add(Integer.toString(i)); } hm.put(1, ar); for(String s:hm.get(1)){ hm.get(1).add("hello"); } } Error Thrown: Exception in thread "main" java.util

问题 Is there any way I can modify the HashMap values of a particular key while iterating over it? A sample program is given below: public static void main(String[] args) { HashMap<Integer,ArrayList<String>> hm = new HashMap<Integer, ArrayList<String>>(); ArrayList<String> ar = new ArrayList<String>(); for(int i=0;i<50;i++){ ar.add(Integer.toString(i)); } hm.put(1, ar); for(String s:hm.get(1)){ hm.get(1).add("hello"); } } Error Thrown: Exception in thread "main" java.util

问题 I have a class like the following: class Test { private LinkedList<Person> persons = new LinkedList<Person>; public synchronized void remove(Person person) { persons.remove(person); } public List<Person> getAllPersons() { // Clients may iterate over the copy returned and modify the structure. return new ArrayList<Person>(persons); } } persons may be modified concurrently: one is via remove() by one thread and two via the shallow copied instance returned by getAllPersons() . I have tested the

问题 This question already has answers here : Iterating through a Collection, avoiding ConcurrentModificationException when removing objects in a loop (24 answers) Why is a ConcurrentModificationException thrown and how to debug it (7 answers) ConcurrentModificationException despite using synchronized (3 answers) Closed 10 months ago . I'm using a Map object in my class that I've synchronized with Collections.synchronizedMap() for a LinkedHashMap like so: private GameObjectManager(){ gameObjects =