小编Den*_*van的帖子

所以我有一个非常奇怪的错误.当我最初使用keySet()迭代大型TreeMap的前10个键时,我偶然发现了它.其中一个键是返回null,就我的理解而言,这是不可能的.所以我在下面写了测试代码:

int i = 0;
        for (Map.Entry<String, Integer> es : sortedMap.entrySet()){
            if (i >= 10) {
                break;
            }

            if (sortedMap.containsKey(es.getKey())){
                System.out.println(es.getKey() + ":" + sortedMap.get(es.getKey()));
            } else {
                System.out.println("Key " + es.getKey() + " does not exist, yet...");
                System.out.println("This does work: " + es.getKey() + ":" + es.getValue());
                System.out.println("This does NOT work: " + es.getKey() + ":" + sortedMap.get(es.getKey()));
            }
            i++;
        }

并获得以下结果:

SOAP:967
'excerpt'::679
'type'::679
Key 'author_url': does not exist, yet...
This does work: 'author_url'::679
This does NOT work: …