移除元素操作

    public static void main(String[] args) {
        Map<String, String> map = new HashMap<>();
        map.put("01", "java");
        map.put("02", "c");
        for (String key : map.keySet()) {
            map.remove(key);
            System.out.println(key);
        }
    }
Exception in thread "main" java.util.ConcurrentModificationException
    at java.util.HashMap$HashIterator.nextNode(HashMap.java:1437)
    at java.util.HashMap$KeyIterator.next(HashMap.java:1461)
    at com.bonatone.shibo.business.controller.BusinessController.main(BusinessController.java:1171)