空指针异常

Question

编译器给出NullPointerException错误，不知道为什么。请帮忙吗？

public List<DBObject> findByDateDescending(int limit) {

    List<DBObject> posts = null;
    // XXX HW 3.2,  Work Here
    // Return a list of DBObjects, each one a post from the posts collection
    DBCursor cur=postsCollection.find().sort(new BasicDBObject("date",-1)).limit(limit);
   while(cur.hasNext()){
/*==>> error */   posts.add(cur.next());
    }//end while 

    return posts;
}

Answer 1

改变这个：

List<DBObject> posts = null;

对此：

List<DBObject> posts = new ArrayList<DBObject>();