java 将Arraylist对象添加到java中的哈希表
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原文地址: http://stackoverflow.com/questions/1753806/
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Adding Arraylist object to hash table in java
提问by venkat
how to store multiple arraylist objects in hashtable in java & how do i get it back.
如何在java中的哈希表中存储多个arraylist对象以及如何取回它。
回答by ChssPly76
Don't. Use HashMapinstead of Hashtable - it's not synchronized.
别。使用HashMap而不是 Hashtable - 它不是同步的。
Map<String, ArrayList<SomeObject>> myMap = new HashMap<String, ArrayList<SomeObject>>();
ArrayList<SomeObject> list = new ArrayList<SomeObject>();
list.add(someObjectInstance1);
list.add(someObjectInstance2);
myMap.put("key1", list); // stores list containing instances #1 and #2 under key "key1"
ArrayList<SomeObject> list2 = new ArrayList<SomeObject>();
list2.add(someObjectInstance3);
myMap.put("key2", list2); // stores list2 containing instance #3 under key "key2"
SomeObject obj1 = myMap.get("key1").get(0); // returns instance #1
SomeObject obj2 = myMap.get("key1").get(1); // returns instance #2
SomeObject obj3 = myMap.get("key2").get(0); // returns instance #3
All that said, you may want to consider using Multimapfrom Google Collectionsinstead:
说了这么多，你可能要考虑使用Multimap之从谷歌集合，而不是：
Multimap<String, ArrayList<SomeObject>> myMap = ArrayListMultimaps.create();
myMap.put("key1", someObjectInstance1);
myMap.put("key1", someObjectInstance2);
myMap.put("key2", someObjectInstance3);
SomeObject obj1 = myMap.get("key1").get(0); // returns instance #1
SomeObject obj2 = myMap.get("key1").get(1); // returns instance #2
SomeObject obj3 = myMap.get("key2").get(0); // returns instance #2
You can see how much more straightforward this approach is.
您可以看到这种方法更加直接。
回答by Geek
Use the Hashcode of each Linklist as the Key. Using a FOR Value mentioned in one of the posts as the Keys is probably not a good idea. What if you have to add a new List somewhere else ? You will have to traverse the entire map to find the next greatest key.
使用每个 Linklist 的 Hashcode 作为 Key。使用其中一篇文章中提到的 FOR 值作为键可能不是一个好主意。如果您必须在其他地方添加新列表怎么办？您必须遍历整个地图才能找到下一个最大的键。
