A volte la tua applicazione potrebbe essere complessa e troppo complessa e alcune funzioni potrebbero avere un effetto collaterale eccessivo. Inoltre, forse un altro thread sta davvero facendo qualcosa di sbagliato in quella lista e non riesci a trovarlo facilmente.
Per il mio problema, ho scritto il mio sistema di liste che delega un altro elenco e, una volta bloccato, tutte le altre modifiche generano ConcurrentModificationException, quindi l'istruzione di modifica errata verrà emessa con l'eccezione. Può anche rilevare gli errori descritti sopra.
import java.util.*;
/**
* Created by IntelliJ IDEA.
* User: francoiscassistat
* Date: 12 juin 2010
* Time: 18:20:18
*
*
* Lockable list, made to debug ConcurrentModificationException on Lists.
* The lock can be switched on/off with setLocked(boolean).
* When locked, all write access to the list or iterators gets ConcurrentModificationException.
* Simple usage case :
*
* list.setLocked(true);
*
* for (Object o : list.iterator()) // now this won't get ConcurrentModificationException, the other instruction that cause this will thrown the exception
* { ... }
*
* list.setLocked(false);
*/
public class LockableList<E> implements List<E> {
protected class LockableListIterator implements Iterator<E> {
protected Iterator<E> iterator;
public LockableListIterator(Iterator<E> iterator) {
this.iterator = iterator;
}
public boolean hasNext() {
return iterator.hasNext();
}
public E next() {
return iterator.next();
}
public void remove() {
checkLock();
iterator.remove();
}
}
protected class LockableListListIterator implements ListIterator<E> {
protected ListIterator<E> listIterator;
public LockableListListIterator(ListIterator<E> listIterator) {
this.listIterator = listIterator;
}
public boolean hasNext() {
return listIterator.hasNext();
}
public E next() {
return listIterator.next();
}
public boolean hasPrevious() {
return listIterator.hasPrevious();
}
public E previous() {
return listIterator.previous();
}
public int nextIndex() {
return listIterator.nextIndex();
}
public int previousIndex() {
return listIterator.previousIndex();
}
public void remove() {
checkLock();
listIterator.remove();
}
public void set(E e) {
checkLock();
listIterator.set(e);
}
public void add(E e) {
checkLock();
listIterator.add(e);
}
}
protected class LockableListSubList implements List<E>
{
protected List<E> list;
public LockableListSubList(List<E> list) {
this.list = list;
}
public int size() {
return list.size();
}
public boolean isEmpty() {
return list.isEmpty();
}
public boolean contains(Object o) {
return list.contains(o);
}
public Iterator<E> iterator() {
return new LockableListIterator(list.iterator());
}
public Object[] toArray() {
return list.toArray();
}
public <T> T[] toArray(T[] a) {
return list.toArray(a);
}
public boolean add(E e) {
checkLock();
return list.add(e);
}
public boolean remove(Object o) {
checkLock();
return list.remove(o);
}
public boolean containsAll(Collection<?> c) {
return list.containsAll(c);
}
public boolean addAll(Collection<? extends E> c) {
checkLock();
return list.addAll(c);
}
public boolean addAll(int index, Collection<? extends E> c) {
checkLock();
return list.addAll(index, c);
}
public boolean removeAll(Collection<?> c) {
checkLock();
return list.removeAll(c);
}
public boolean retainAll(Collection<?> c) {
checkLock();
return list.retainAll(c);
}
public void clear() {
checkLock();
list.clear();
}
@Override
public boolean equals(Object o) {
return list.equals(o);
}
@Override
public int hashCode() {
return list.hashCode();
}
public E get(int index) {
return list.get(index);
}
public E set(int index, E element) {
checkLock();
return list.set(index, element);
}
public void add(int index, E element) {
checkLock();
list.add(index, element);
}
public E remove(int index) {
checkLock();
return list.remove(index);
}
public int indexOf(Object o) {
return list.indexOf(o);
}
public int lastIndexOf(Object o) {
return list.lastIndexOf(o);
}
public ListIterator<E> listIterator() {
return new LockableListListIterator(list.listIterator());
}
public ListIterator<E> listIterator(int index) {
return new LockableListListIterator(list.listIterator(index));
}
public List<E> subList(int fromIndex, int toIndex) {
return new LockableListSubList(list.subList(fromIndex, toIndex));
}
}
protected List<E> list;
protected boolean locked;
public LockableList(List<E> list) {
this.list = list;
locked = false;
}
public boolean isLocked() {
return locked;
}
public void setLocked(boolean locked) {
this.locked = locked;
}
protected void checkLock() {
if (locked)
throw new ConcurrentModificationException("Locked");
}
public int size() {
return list.size();
}
public boolean isEmpty() {
return list.isEmpty();
}
public boolean contains(Object o) {
return list.contains(o);
}
public Iterator<E> iterator() {
return new LockableListIterator(list.iterator());
}
public Object[] toArray() {
return list.toArray();
}
public <T> T[] toArray(T[] a) {
return list.toArray(a);
}
public boolean add(E e) {
checkLock();
return list.add(e);
}
public boolean remove(Object o) {
checkLock();
return list.remove(o);
}
public boolean containsAll(Collection<?> c) {
return list.containsAll(c);
}
public boolean addAll(Collection<? extends E> c) {
checkLock();
return list.addAll(c);
}
public boolean addAll(int index, Collection<? extends E> c) {
checkLock();
return list.addAll(index, c);
}
public boolean removeAll(Collection<?> c) {
checkLock();
return list.removeAll(c);
}
public boolean retainAll(Collection<?> c) {
checkLock();
return list.retainAll(c);
}
public void clear() {
checkLock();
list.clear();
}
@Override
public boolean equals(Object o) {
return list.equals(o);
}
@Override
public int hashCode() {
return list.hashCode();
}
public E get(int index) {
return list.get(index);
}
public E set(int index, E element) {
checkLock();
return list.set(index, element);
}
public void add(int index, E element) {
checkLock();
list.add(index, element);
}
public E remove(int index) {
checkLock();
return list.remove(index);
}
public int indexOf(Object o) {
return list.indexOf(o);
}
public int lastIndexOf(Object o) {
return list.lastIndexOf(o);
}
public ListIterator<E> listIterator() {
return new LockableListListIterator(list.listIterator());
}
public ListIterator<E> listIterator(int index) {
return new LockableListListIterator(list.listIterator(index));
}
public List<E> subList(int fromIndex, int toIndex) {
return new LockableListSubList(list.subList(fromIndex, toIndex));
}
}
Basta usare in questo modo:
List list = new LockableList(new ArrayList(...));
list.setLocked(true);
for (E e : list.iterator())
{ ... }
list.setLocked(false);
Spero che possa aiutare qualcun altro.
fonte
2010-06-12 23:09:00
Possibile duplicato di [Iterazione attraverso una raccolta, evitando ConcurrentModificationException durante la rimozione in loop] (http://stackoverflow.com/questions/223918/iterating-through-a-collection-avoiding-concurrentmodificationexception- al momento) – Raedwald