java - Concurrent Modification Exception : adding to an ArrayList -

the problem occurs @

element element = it.next(); 

and code contains line, inside of ontouchevent

for (iterator<element> = melements.iterator(); it.hasnext();){     element element = it.next();      if(touchx > element.mx  && touchx < element.mx + element.mbitmap.getwidth() && touchy > element.my                && touchy < element.my + element.mbitmap.getheight()) {            //irrelevant stuff..          if(element.cflag){             melements.add(new element("crack",getresources(), (int)touchx,(int)touchy));             element.cflag = false;          }                } } 

all of inside synchronized(melements), melements arraylist<element>

when touch element, may activate cflag, create element different properties, fall off screen , destroy in less second. it's way of creating particle effects. can call "particle" crack, string parameter in constructor.

this works fine until add main element. have 2 elements on screen @ same time, , if touch newest element, works fine, , launches particles.

however, if touch , activate cflag on older element, gives me exception.

 07-28 15:36:59.815: error/androidruntime(4026): fatal exception: main 07-28 15:36:59.815: error/androidruntime(4026): java.util.concurrentmodificationexception 07-28 15:36:59.815: error/androidruntime(4026):     @ java.util.arraylist$arraylistiterator.next(arraylist.java:573) 07-28 15:36:59.815: error/androidruntime(4026):     @ com.juggle2.panel.ontouchevent(panel.java:823) 07-28 15:36:59.815: error/androidruntime(4026):     @ android.view.view.dispatchtouchevent(view.java:3766) 07-28 15:36:59.815: error/androidruntime(4026):     @ android.view.viewgroup.dispatchtouchevent(viewgroup.java:863) 07-28 15:36:59.815: error/androidruntime(4026):     @ android.view.viewgroup.dispatchtouchevent(viewgroup.java:863) 07-28 15:36:59.815: error/androidruntime(4026):     @ com.android.internal.policy.impl.phonewindow$decorview.superdispatchtouchevent(phonewindow.java:1767) 07-28 15:36:59.815: error/androidruntime(4026):     @ com.android.internal.policy.impl.phonewindow.superdispatchtouchevent(phonewindow.java:1119) 07-28 15:36:59.815: error/androidruntime(4026):     @ android.app.activity.dispatchtouchevent(activity.java:2086) 07-28 15:36:59.815: error/androidruntime(4026):     @ com.android.internal.policy.impl.phonewindow$decorview.dispatchtouchevent(phonewindow.java:1751) 07-28 15:36:59.815: error/androidruntime(4026):     @ android.view.viewroot.handlemessage(viewroot.java:1785) 07-28 15:36:59.815: error/androidruntime(4026):     @ android.os.handler.dispatchmessage(handler.java:99) 07-28 15:36:59.815: error/androidruntime(4026):     @ android.os.looper.loop(looper.java:123) 07-28 15:36:59.815: error/androidruntime(4026):     @ android.app.activitythread.main(activitythread.java:4627) 07-28 15:36:59.815: error/androidruntime(4026):     @ java.lang.reflect.method.invokenative(native method) 07-28 15:36:59.815: error/androidruntime(4026):     @ java.lang.reflect.method.invoke(method.java:521) 07-28 15:36:59.815: error/androidruntime(4026):     @ com.android.internal.os.zygoteinit$methodandargscaller.run(zygoteinit.java:893) 07-28 15:36:59.815: error/androidruntime(4026):     @ com.android.internal.os.zygoteinit.main(zygoteinit.java:651) 07-28 15:36:59.815: error/androidruntime(4026):     @ dalvik.system.nativestart.main(native method) 

how can make work?

concurrentmodificationexception occurs when modify list (by adding or removing elements) while traversing list iterator.

try

list<element> thingstobeadd = new arraylist<element>(); for(iterator<element> = melements.iterator(); it.hasnext();) {     element element = it.next();     if(...) {           //irrelevant stuff..         if(element.cflag){             // melements.add(new element("crack",getresources(), (int)touchx,(int)touchy));             thingstobeadd.add(new element("crack",getresources(), (int)touchx,(int)touchy));             element.cflag = false;         }                } } melements.addall(thingstobeadd ); 

also should consider enhanced each loop jon suggested.