从一个ArrayList删除元素，如果他们在一个又一个present不提高ConcurrentModificationException的 [英] Remove elements from an Arraylist if they are present in another one without raising ConcurrentModificationException

问题描述

下面是code：

Ledger obj = null;
MyUtilPojo obj1 = null;
Iterator it = toList.iterator();
while (it.hasNext()) {
    obj = (Ledger) it.next(); //after first iteration next here produce an error
    Iterator it1 = moreToList.iterator();
    while (it1.hasNext()) {
        obj1 = (MyUtilPojo) it1.next();
        if (obj.getId() == obj1.getKey()) {
            toList.remove(obj);                                
        }
    }
}

这引发错误 ConcurrentModificationException的，可有人能帮助？

This raise an error ConcurrentModificationException, can someone help?

推荐答案

当您修改列表（通过添加或删除元素），而穿越与迭代器列表时发生ConcurrentModificationException的。

ConcurrentModificationException occurs when you modify the list (by adding or removing elements) while traversing a list with Iterator.

    Ledger obj = null;
    MyUtilPojo obj1 = null;
    List thingsToBeDeleted = new ArrayList();

    Iterator it = toList.iterator();
    while (it.hasNext()) {
        obj = (Ledger) it.next();
        Iterator it1 = moreToList.iterator();
        while (it1.hasNext()) {
            obj1 = (MyUtilPojo) it1.next();
            if (obj.getId() == obj1.getKey()) {
                thingsToBeDeleted.add(obj);    // put things to be deleted                            
            }
        }
    }
    toList.removeAll(thingsToBeDeleted);

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