Implementing a best match search in Java

Question

I am trying to get a best match string matching to work using existing Java data structures. It is quite slow though, any suggestions to improve its performance will be welcomed

Answer 1

Use a TreeMap and the floorEntry(K key) method:

Returns a key-value mapping associated with the greatest key less than or equal to the given key, or null if there is no such key.

The following is simplified. Real code would need to search if an invalid entry is found, e.g. if the map had a key 0060175551000, in which case you'd need to find the common prefix between the search key and the found key, then do the lookup again. Rinse and repeat.

TreeMap map = new TreeMap<>();
map.put("0060175559138", "VIP");
map.put("006017555"    , "National");
map.put("006017"       , "Local");
map.put("0060"         , "X");

String key = "0060175552020";
Entry entry = map.floorEntry(key);
if (entry == null)
    System.out.println("Not found: " + key);
else {
    System.out.println(key);
    System.out.println(entry);
}

Output

0060175552020
006017555=National

---

UPDATE There is the full code, with loop for extended search.

private static Entry lookup(NavigableMap map, String key) {
    String keyToFind = key;
    for (;;) {
        Entry entry = map.floorEntry(keyToFind);
        if (entry == null)
            return null;
        String foundKey = entry.getKey();
        int prefixLen = 0;
        while (prefixLen < keyToFind.length() && prefixLen < foundKey.length() &&
               keyToFind.charAt(prefixLen) == foundKey.charAt(prefixLen))
            prefixLen++;
        if (prefixLen == 0)
            return null;
        if (prefixLen == foundKey.length())
            return entry;
        keyToFind = key.substring(0, prefixLen);
    }
}

Test

TreeMap map = new TreeMap<>();
map.put("0060175559138", "VIP");
map.put("0060175551000", "Other");
map.put("006017555"    , "National");
map.put("006017"       , "Local");
map.put("0060"         , "X");

System.out.println(lookup(map, "0060175559138"));
System.out.println(lookup(map, "0060175552020"));
System.out.println(lookup(map, "0055708570068"));
System.out.println(lookup(map, "8684064893870"));

Output

0060175559138=VIP
006017555=National
null
null