在Map或者Collection的时候，不要用它们的API直接修改集合的内容，如果要修改可以用Iterator的remove()方法，例如：

    public void setReparation( Reparation reparation ) {
        for (Iterator it = this.reparations.iterator();it.hasNext();){    //reparations为Collection
            Reparation repa = (Reparation)it.next();
            if (repa.getId() == reparation.getId()){
                this.reparations.remove(repa);
                this.reparations.add(reparation);
            }
        }
   }

如上写会在运行期报ConcurrentModificationException，可以如下修改：

    public void setReparation( Reparation reparation ) {
        boolean flag = false;
        for (Iterator it = this.reparations.iterator();it.hasNext();){    //reparations为Collection
            Reparation repa = (Reparation)it.next();
            if (repa.getId() == reparation.getId()){
                it.remove();
                flag = true;
                break;
            }
        }
        if(flag){
          this.reparations.add(reparation);
        }
    }

具体可以参考：http://gceclub.sun.com.cn/yuanchuang/week-14/iterator.html