java - 尝试从列表中删除元素时出现 ConcurrentModificationException

Question

这个问题已经有答案了:

Iterating through a Collection, avoiding ConcurrentModificationException when removing objects in a loop (31 个回答)

已关闭 8 年前。

嗯，我已经阅读了其他帖子，但无法解决我的问题。我的 ManagedBean 中有一个 dataTable (JSF) 绑定(bind)。我有一个选定元素的列表，我想删除这些元素，请参阅:

public void removeSelected() {

    for (Map.Entry<Integer, Boolean> entry : registrosSelecionados.entrySet()){
       if (entry.getValue() == true){
           int id = entry.getKey();
           Iterator<Bean> it = beans.iterator();
           while(it.hasNext()){
           Bean b = it.next();
           if (b.getId().equals(id)){
               setBean(b);
               deletar();
           }
           }
       }
    }
    }

我上面的方法调用了另一个名为“deletar()”的方法，请参阅:

 public void deletar() {
    try {


        //Se o bean for nulo então capturamos o bean selecionado no DataTable, se este existir
        if (bean == null){
        if (dataTable == null){
            throw new RuntimeException("O bean é nulo e não há dataTable vinculado ao ManagedBean. A deleção será abortada");
        }
        bean = (Bean) dataTable.getRowData();
        }

        beforeRemove();
        getBoPadrao().delete((AbstractBean) bean);
        addInfoMessage("Registro deletado com sucesso");
        beans.remove(bean);
        bean = null;
        afterRemove();
    } catch (BOException e) {
        addErrorMessage(e.getMessage());
        FacesContext.getCurrentInstance().validationFailed();
    } catch (Exception e) {
        e.printStackTrace();
        logger.error((new StringBuilder()).append("Erro ao deletar: ")
            .append(e.getMessage()).toString());
        FacesContext.getCurrentInstance().validationFailed();
        addErrorMessage((new StringBuilder()).append("Erro ao deletar. ")
            .append(e.getMessage()).toString());
    }
    }

Bean 已从数据库中删除，但是当尝试从“列表”中删除时出现错误:

Jan 31, 2015 5:38:32 PM com.sun.faces.context.AjaxExceptionHandlerImpl handlePartialResponseError
Grave: java.util.ConcurrentModificationException
    at java.util.ArrayList$Itr.checkForComodification(ArrayList.java:859)
    at java.util.ArrayList$Itr.next(ArrayList.java:831)
    at br.com.jwebbuild.mb.BasicCrudMBImpl.removeSelected(BasicCrudMBImpl.java:226)

编辑1

我尝试编辑我的 deletar() 方法，放置一个迭代器来删除元素，但没有成功，错误仍然存​​在。

public void deletar() {
    try {


        //Se o bean for nulo então capturamos o bean selecionado no DataTable, se este existir
        if (bean == null){
        if (dataTable == null){
            throw new RuntimeException("O bean é nulo e não há dataTable vinculado ao ManagedBean. A deleção será abortada");
        }
        bean = (Bean) dataTable.getRowData();
        }

        beforeRemove();
        getBoPadrao().delete((AbstractBean) bean);
        addInfoMessage("Registro deletado com sucesso");

        Iterator<Bean> it = beans.iterator();
        while (it.hasNext()) {
        Bean b = it.next();
        if (b.equals(bean)) {
            it.remove();
        }
        }

        bean = null;
        afterRemove();

Answer 1

你说，

Well, i already read the others posts and can't solve my problem.

如果您阅读过其他类似的文章，那么您应该已经知道您只能使用迭代器进行删除，这是您没有做的事情，而这正是您必须做的。

例如，

public void deltar(Iterator<Bean> it, Bean bean) {
   // ..... 
   it.remove();
}