Map遍历操作

>>>>>>>>>>>>>>正确方法:
Iterator<Entry<String, ArrayList<String>>> blockIterator = blockMap.entrySet().iterator();
        while(blockIterator.hasNext()){
            Entry<String, ArrayList<String>> entry= blockIterator.next();
            String key_date = entry.getKey();
            if(key_date.compareTo(sformat.format(date))<=0){
                blockIterator.remove();
            }
        }

>>>>>>>>>>>这个方法是错误的!!!!!!!!
        for(String key_date : blockMap.keySet()){
            if(key_date.compareTo(sformat.format(date))<=0){
                blockMap.remove(key_date);,//不能再迭代的时候删除!!!;
            }
        }