How can I find a key in a map based on a pattern matching in java?

Question

I want to find keys in a map with a pattern matching.

Ex:-        Map<String, String> map = new HashMap<String, String>();     map.put("address1", "test test test");     map.put("address2", "aaaaaaaaaaa");     map.put("fullname", "bla bla"); 

From above map, I want to get the values of keys which has prefix of "address". So as in this example output should be the first two results ("address1" and "address2").

How can I achieve this dynamically?

Answer 1

You can grab the keySet of the map and then filter to get only keys that starts with "address" and add the valid keys to a new Set.

With Java 8, it's a bit less verbose:

Set<String> set = map.keySet()                      .stream()                      .filter(s -> s.startsWith("address"))                      .collect(Collectors.toSet());