Java map.get(key) - automatically do put(key) and return if key doesn't exist?

Question

I am sick of the following pattern:

value = map.get(key);
if (value == null) {
    value = new Object();
    map.put(key, value);
}

This ex

Answer 1

EDIT : Note that the feature mentioned below is long deprecated, and a CacheBuilder should be used instead.

The Guava library has a "computing map", see MapMaker.makeComputingMap(Function).

Map map = new MapMaker().makeComputingMap(
    new Function() {
      public String apply(Stringt) {
        return new Object();
      }
  });

If you need the Function several times, extract it into a utility class, and then create the Map like this (where MyFunctions.NEW_OBJECT is the static Function instance):

Map map = new MapMaker()
    .makeComputingMap(MyFunctions.NEW_OBJECT);