Set集合使用注意tips

Set中的某些元素，当时使用边遍历，边删除的方法，报了以下异常：

ConcurrentModificationException

example:
    Set<CheckWork> set = this.getUserDao().getAll(qf).get(0).getActionCheckWorks();
    for(CheckWork checkWork : set){
        if(checkWork.getState()==1){
            set.remove(checkWork);
        }
    }

解决方案：

1. 遍历删除List

   List<CheckWork> list = this.getUserDao().getAll();
   Iterator<CheckWork> chk_it = list.iterator();
   while(chk_it.hasNext()){
       CheckWork checkWork = chk_it.next();
       if(checkWork.getPlanState()==1){
           chk_it.remove();
       }
   }
   

2. 遍历删除Set

   Set<CheckWork> set =  this.getUserDao().getAll().get(0).getActionCheckWorks();
           Iterator<CheckWork> it = set.iterator();
           while(it.hasNext()){
               CheckWork checkWork = it.next();
               if(checkWork.getState()==1){
                   it.remove();
               }
           }
   

3. 遍历删除Set

   Set<CheckWork> set = this.getUserDao().getAll(qf).get(0).getActionCheckWorks()；
   Set<CheckWork> delSet=new HashSet<>();
   for(CheckWork checkWork : set){
       if(checkWork.getState()==1){
           delSet.add(checkWork);
       }
   }
   set.removeAll(delSet);