Question

What is the best practice in implementing/providing getters/setters for a class containing a map?

The most common implementation I see is:

public class MyClass {

  private Map<String, String> myMap;
  public getMyMap() { /* Return an unmodifiable map */ }
  public setMyMap(Map<String, String> myMap) { ... }
}

Or would it be better to provide an interface like:

public getMyMap() { /* Return a modifiable map */ }
public addToMap(String key, String value) { myMap.put(key, value); }

And why is such method better?

Answer 1

Both have their uses. The methods exposed by a class should be of a proper level of abstraction. For example if the class is a registry of dogs backed by a Map<String, Dog>, then it could provide methods like:

void addDog(String name, Dog dog);
Dog findByName(String name);

If it’s say a rule engine that allows clients to specify the entire rule set in one call, then it could expose methods like:

void setRules(Map<String, Rule> rules);
Map<String, Rule> getRules();