Java: HashMap: get: specify default value

I reckon that... Object o = map.get("x"); if(o == null) o = BOOLEAN.TRUE; ... is pretty much the most readable and efficient way of doing this. You're only doing one map lookup this way. Unfortunately, "Java" and "terse" don't tend to fit in the same sentence unless it's a negative.

OP Edited his question, but I'll leave the answer just in case. You should use map.containsKey("x") instead of map.get("x") != null to test if map has a mapping for key. Maps can contain null as valid value in mapping. The same goes for python. It's not enough to test if dict[key] == None to know if a key is mapped to something. Quick test: d = {'a': None} # returns True d['a'] == None # raises KeyError d['b'] # returns 'Whatever' d.get('b', 'Whatever') So java equivalent to python dict.get() is map.containsKey("x") ? map.get("x") : default_value as OP said

Both are valid solutions (although introducing a local variable would probably be better...performance-wise) but it's not a good idea to do this everywhere in your code. Consider writing an adapter for HashMap that provides you with a new get() method that allows you to specify a default value. That's the best way to enhance the functionality of a class.

map.get("x") == null ? true : map.get("x") This sounds good but if you need it extensively you can implement your own implementation to handle this in get() itlself

I'd extend the map to expose a get(String key, Boolean defaultValue)... if not that I'd atleast put the terniary in a method, pushing the result of get.("x") onto the stack, instead of getting it twice... something like IfNull(map.get("x"), True) If you need to provide default you probably have a "specialised" use for the map anyway, hence I guess the wrapper-class would be the way to go, not just for this behaviour, but for any other (current AND FUTURE) specialised behaviours/responsibilities. That's just how I'd tackle it... I'm NO object-oriented design guru though ;-) Cheers. Keith.

A short and reasonably generic way to do it, although not necessarily good practice, would be a helper class and a static import: Helper.java package vlad; import java.util.Map; public class Helper{ public static <K,V> V get(Map<K,V> m, K key, V def){ V v = m.get(key); return (v!=null) ? v : def; } } Test.java import java.util.*; import static vlad.Helper.get; class Test{ public static void main(String[]args){ Map<String, Integer> m = new HashMap<String,Integer>(); m.put("forty-two", 42); m.put("three", 3); m.put("one", 1); System.out.println(get(m,"forty-two",-1)); System.out.println(get(m,"three",-1)); System.out.println(get(m,"one",-1)); System.out.println(get(m,"something_else",-1)); } }