解决Concurrent Modification Exception

原因：一个线程在用迭代器iterator的同时，另一个线程又在修改list数据

一种解决办法是

synchronize all access to the List, using the list itself as the monitor

code:

---

synchronized (list) {
    for (Iterator it = list.iterator(); it.hashNext(); ) {
        Foo f = (Foo) it.next();
        // do what you need with f
    }
}

---

Whatever other threads are modifying the list, they need to be synchronized too, also on the list. E.g.:

code:

---

syncronized (list) {
    list.add(new Foo());
}

---

or

code:

---

syncronized (list) {
    list.remove(oldFoo);
}