HashMap Search for part of an key? [duplicate]

Answer 1

You can try this approach:

public Map<String,Integer> filterMap(Map<String, Integer> inputMap){
    Map<String, Integer> resultHashMap = new HashMap<String, Integer>();
        for (String key : inputMap.keySet()) {
            if(key.length()==5){
                resultHashMap.put(key,inputMap.get(key));
            }   
        }
        return resultHashMap;
    }

Answer 2

With HashMap<String, Integer> you can only go through keySet() and do contains() for String keys and your pattern.

Answer 3

Map<String, Integer> result = new HashMap<String, Integer>;
for(String key : yourMap.keySet()) {
    if(key.length() == 4){
        result.put(key, yourMap.get(key);
    }
}

After executing this code you have all key/value pairs with 4 letter keys in result.

Answer 4

As has been noted, there isn't a terribly efficient* way to do it with the datastructure you have specified. However, if you add an additional Map<Integer, List<String>> to keep track of the mapping from string length to the list of all keys with that length, then you will be able to do this very efficiently.

*Using just the Map<String, Integer>, you would need to iterate through the entire capacity of the larger map, whereas adding this supplemental datastructure would impose an O(1) lookup (assuming you used a HashMap) followed by iteration through just the result set, which is the fastest possible outcome.

Answer 5

Set<Entry<String, Integer>> s1 = map.entrySet();
    for (Entry<String, Integer> entry : s1) {
          if(entry.getKey().length == 4)
          //add it to a map;
}

First get the entry set to your hashmap. Iterate through the set and check the length of each key and add it to a map or use it as u want it.

Answer 6

You cannot do this via HashMap, you should write your own implementation for Map for implementing string length based searching in a map.