java.util.ConcurrentModificationException的解决办法

使用Iterator来迭代的代码如下：
public String findByEvent() throws Exception {
        try {
            eventName = new String(eventName.getBytes("iso-8859-1"), "UTF-8");
            listGroupInfo = this.groupInfoService.findByEvent(eventName);
                        Iterator<GroupInfo> iter = listGroupInfo.iterator();
            if (listGroupInfo.size() != 0) {
                GroupInfo groupInfo = iter.next();
                for (int i = 0; i < listGroupInfo.size() - 1; i++) {
                    for (int j = listGroupInfo.size() - 1; j > i; j--) {
                        if (listGroupInfo.get(j).getGroupNumber().equals(
                                listGroupInfo.get(i).getGroupNumber())) {
                            listGroupInfo.remove(j);
                        }
                    }
                }

            }
        } catch (Exception e) {
            // TODO: handle exception
            e.printStackTrace();
            return INPUT;
        }
        return SUCCESS;

    }
上面的代码运行正常！
本次使用的源代码如下：

public String findUnit() throws Exception {
        try {

            Map session = ActionContext.getContext().getSession();
            String ids = session.get("userId").toString();
            id = Long.parseLong(ids);
            listAthlete = this.athleteService.findByUserId(id);
            listUnitInfo = this.unitInfoService.findByUserId(id);
            for(UnitInfo unitInfo :listUnitInfo){
                for(Athlete athlete:listAthlete){
                    if(athlete.getUnitGroup().getUnitInfo().getName().equals(unitInfo.getName())){
                        System.out.println("移除:"+unitInfo.getName());
                        listAthlete.remove(athlete);
                        listUnitInfo.remove(unitInfo);

                    }
                }
            }
        } catch (Exception e) {
            e.printStackTrace();
            System.out.print(e);
            return INPUT;
        }
        return SUCCESS;
    }

使用的是foreach，因为大家都知道使用foreach为我们带来了极大的方便，所以考虑使用foreach也是正常的思路。但是，使用的时候，却产生了如下的异常。

java.util.ConcurrentModificationException
java.util.ConcurrentModificationException
    at java.util.AbstractList$Itr.checkForComodification(AbstractList.java:372)
    at java.util.AbstractList$Itr.next(AbstractList.java:343)
    at com.yaxing.action.AthleteAction.findUnit(AthleteAction.java:398)
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
    at java.lang.reflect.Method.invoke(Method.java:597)
    at com.opensymphony.xwork2.DefaultActionInvocation.invokeAction(DefaultActionInvocation.java:452)
    at com.opensymphony.xwork2.DefaultActionInvocation.invokeActionOnly(DefaultActionInvocation.java:291)
    at com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:254)
    at com.opensymphony.xwork2.interceptor.DefaultWorkflowInterceptor.doIntercept(DefaultWorkflowInterceptor.java:176)
    at com.opensymphony.xwork2.interceptor.MethodFilterInterceptor.intercept(MethodFilterInterceptor.java:98)
    at com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:248)
    at com.opensymphony.xwork2.validator.ValidationInterceptor.doIntercept(ValidationInterceptor.java:263)
    at org.apache.struts2.interceptor.validation.AnnotationValidationInterceptor.doIntercept(AnnotationValidationInterceptor.java:68)
    at com.opensymphony.xwork2.intercept

补充：软件开发 , Java ,