在Map或者Collection的時候，不要用它們的API直接修改集合的內容，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為Collection
??????????? Reparation repa = (Reparation)it.next();
??????????? if (repa.getId() == reparation.getId()){
??????????????? this.reparations.remove(repa);
????????????????this.reparations.add(reparation);
??????????? }
??????? }
?? }

如上寫會在運行期報ConcurrentModificationException，可以如下修改：

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

具體可以參考：http://gceclub.sun.com.cn/yuanchuang/week-14/iterator.html