java.util.ConcurrentModificationException

??? 今日在調試程序時，出現了?java.util.ConcurrentModificationException，出錯代碼如下：

for(Iterator?ite?=?candidateObjDtoList.iterator();?ite.hasNext();?)?

{

???????CandidateObjDto?dto?=?(CandidateObjDto)ite.next();

???????if(dto.getType()?==?Constants.CANDIDATE_OBJ_TYPE_SET)?

{

????????????????dto.setVoteType(Constants.VOTE_TYPE_ABSTAIN);

???????}?else?

{

???????????????candidateObjDtoList.remove(dto);????????

??????}

}

????? 在網上搜索到資料如下：

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);

????????}

????}

???? 成功解決了所遇問題，成功后的代碼如下：
?

for(Iterator?ite?=?candidateObjDtoList.iterator();?ite.hasNext();?)?

{

????????CandidateObjDto?dto?=?(CandidateObjDto)ite.next();

????????if(dto.getType()?==?Constants.CANDIDATE_OBJ_TYPE_SET)?

{

????????????????dto.setVoteType(Constants.VOTE_TYPE_ABSTAIN);//對該候選項投棄權票

????????}?else?

{

?????????????????ite.remove();

????????}

}????

???????????????????????????????????????????????????????????????????????????????????????????????? 阿蜜果發表于 2007年01月26日 10:51:00
??????????????????????????????????????????????????????????? 地址：http://blog.csdn.net/amigoxie/archive/2007/01/26/1494401.aspx

posted on 2007-02-11 23:40 阿蜜果閱讀(8958) 評論(9) 編輯收藏所屬分類: Java

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