Java将Hashmap放入Treemap中
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Java putting Hashmap into Treemap
提问by BeyondProgrammer
I am currently reading 2 million lines from a textfile as asked in the previous question Java Fastest way to read through text file with 2 million lines
我目前正在从文本文件中读取 200 万行，如上一个问题 Java Fastest way to read through text file with 200万行
Now I store these information into HashMap and I want to sort it via TreeMap because I want to use ceilingkey. Is the following method correct?
现在我将这些信息存储到 HashMap 中，我想通过 TreeMap 对其进行排序，因为我想使用天花板键。以下方法是否正确？
private HashMap<Integer, String> hMap = new HashMap();
private TreeMap<Integer, String> tMap = new TreeMap<Integer, String>(hMap);
采纳答案by Akkusativobjekt
HashMap<Integer, String> hashMap = new HashMap<Integer, String>();
TreeMap<Integer, String> treeMap = new TreeMap<Integer, String>();
treeMap.putAll(hashMap);
Should work anyway.
无论如何都应该工作。
回答by husayt
This would work just fine:
这将工作得很好：
HashMap<Integer, String> hashMap = new HashMap<>();
TreeMap<Integer, String> treeMap = new TreeMap<>(hashMap);
But I wouldn't advise using HashMapto store the input. You end up with two Maps holding the same huge data. Either do it on the fly and add directly into TreeMapor use Listto TreeMapconversion.
但我不建议使用HashMap来存储输入。您最终会得到两个包含相同庞大数据的 Map。无论是做对飞，并直接加入到TreeMap或使用List到TreeMap的转换。
Also, for even more efficiency consider primitive collections.
此外，为了提高效率，请考虑使用原始集合。
回答by Nagmani Verma
HashMap<Integer, String> hashMap = new HashMap<Integer, String>();
TreeMap<Integer, String> treeMap = new TreeMap<Integer, String>();
hashMap.remove(null);
treeMap.putAll(hashMap);
HashMap will allow null but TreeMap not so before adding into Treemap, remove null from keyset
在添加到 Treemap 之前，HashMap 将允许 null 但 TreeMap 不允许，从键集中删除 null
