我想从具有内部映射和外部映射关系的哈希映射创建哈希映射吗？

Question

public interface InnerMap<V> extends Map<String, V> {
    Map<String, V> getInnerMap(String prefix);
}

For example:

baseMap.put("aabb", "one");
baseMap.put("aabbddd", "two");
InnerMap map1 = baseMap.getInnerMap("aa");
map1.get("bb") => "one"
map1.get("bbdd") => "two"
map1.get("aa") => null
map2 = map1.getInnerMap("bb");
map2.get("dd") => "two"

and also want to override put and get method

Answer 1

It would be hard to keep track of all possible inner maps. There is no doubt a much more efficient solution than mine if you indexed keys and such like. However, if quick and dirty works for you, try this. You didn't mention a language so you're getting Java - hope I guessed right!

import java.util.HashMap;
import java.util.Map.Entry;

public class InnerMap extends HashMap<String, String> {

    public InnerMap getInnerMap(String key) {
        InnerMap innerMap = new InnerMap();
        for (Entry<String, String> entry : entrySet()) {
            String existingKey = entry.getKey();
            String value = entry.getValue();
            if (existingKey.startsWith(key)) {
                String newKey = existingKey.substring(key.length());
                innerMap.put(newKey, value);
            }
        }
        return innerMap;
    }

}

public class Test {
    public static void main(String[] args) {
        InnerMap baseMap = new InnerMap();
        baseMap.put("aabb", "one");
        baseMap.put("aabbdd", "two");
        InnerMap map1 = baseMap.getInnerMap("aa");
        System.out.println(map1.get("bb"));// => "one"
        System.out.println(map1.get("bbdd"));// => "two"
        System.out.println(map1.get("aa"));// => null
        InnerMap map2 = map1.getInnerMap("bb");
        System.out.println(map2.get("dd"));// => "two"
    }
}

Answer 2

It sounds like you want a Trie-like structure. (Pronounce that "try", to avoid insanity.)

http://code.google.com/p/patricia-trie/