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javaiteratorappletconcurrentmodificationremove-method

Java applet throws error in remove object from Iterator array

Welcome, i am programming a simple RPG game in java applet. It is getting more and more complicated and many errors are thrown to my face. Today i have problem with .remove(); method.

Exception in thread "AWT-EventQueue-1" java.util.ConcurrentModificationException
    at java.util.ArrayList$Itr.checkForComodification(Unknown Source)
    at java.util.ArrayList$Itr.remove(Unknown Source)
    at rpg.main.paint(main.java:365)
    at rpg.main.update(main.java:331)
    at sun.awt.RepaintArea.updateComponent(Unknown Source)
    at sun.awt.RepaintArea.paint(Unknown Source)
    at sun.awt.windows.WComponentPeer.handleEvent(Unknown Source)
    at java.awt.Component.dispatchEventImpl(Unknown Source)
    at java.awt.Container.dispatchEventImpl(Unknown Source)
    at java.awt.Component.dispatchEvent(Unknown Source)
    at java.awt.EventQueue.dispatchEventImpl(Unknown Source)
    at java.awt.EventQueue.access$200(Unknown Source)
    at java.awt.EventQueue$3.run(Unknown Source)
    at java.awt.EventQueue$3.run(Unknown Source)
    at java.security.AccessController.doPrivileged(Native Method)
    at java.security.ProtectionDomain$1.doIntersectionPrivilege(Unknown Source)
    at java.security.ProtectionDomain$1.doIntersectionPrivilege(Unknown Source)
    at java.awt.EventQueue$4.run(Unknown Source)
    at java.awt.EventQueue$4.run(Unknown Source)
    at java.security.AccessController.doPrivileged(Native Method)
    at java.security.ProtectionDomain$1.doIntersectionPrivilege(Unknown Source)
    at java.awt.EventQueue.dispatchEvent(Unknown Source)
    at java.awt.EventDispatchThread.pumpOneEventForFilters(Unknown Source)
    at java.awt.EventDispatchThread.pumpEventsForFilter(Unknown Source)
    at java.awt.EventDispatchThread.pumpEventsForHierarchy(Unknown Source)
    at java.awt.EventDispatchThread.pumpEvents(Unknown Source)
    at java.awt.EventDispatchThread.pumpEvents(Unknown Source)
    at java.awt.EventDispatchThread.run(Unknown Source)

That's how error log looks like. Code of program:

main.java

As we can see error appears in paint methid in the end of program, but i dont know maybe it is caused by wrong initiation in the beginning of program?

public void initLocatables()
public void initLocatables2()

And i have to admit that they are called in main while loop in run method. These is place where error apears, and below in comment i have included previous method that has also thrown error, both in remove();

for (Iterator i = locatablesArray.listIterator(); i.hasNext();) {
               Locatable l = (Locatable) i.next(); 
               l.draw(g);
               i.remove();
            }
/*while(itrLocatables.hasNext())
{
    Locatable l = itrLocatables.next();
    l.draw(g);
    l.remove();
}*/

Thank you for any reply.

Solution

  • Maybe when you call repaint() in run(), paint() is queued to EDT and called as soon as possible; while iterating locatablesArray a call to initLocatables2() in run() is done another time and the re-init of locatablesArray in the same time the code of paint() will produce the error.
    My advice is to separate init operation in a specific init section and call it once, the run your main loop.

    Just another thing: why are you init a Iterator (class field itrLocatables) in initLocatables2()? Use iterator when needed if possible.

    Hope to be clear, English is not my native language.