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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?
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You should not include getters and setters in your diagram until they do something special: null checking and so on. But it is a sign of bad design, so general answer is "No, you should not".
Getters and setters are used to protect your data, particularly when creating classes. For each instance variable, a getter method returns its value while a setter method sets or updates its value. Given this, getters and setters are also known as accessors and mutators, respectively.
To fix this, you need to pass a reference to the GetterAndSetter instance from class A to B . You can do this e.g. by passing it as a parameter to a method of B , or by creating a new instance of A in B and calling a method that provides an instance of GetterAndSetter .
The Java coding convention states that methods (getters and setters are methods) should be after constructors declarations. It just a convention and it exists to make code easier to read in general.
In general I would say try not to return the map at all. Have a method that takes the key and returns the value. Taking a map is ok, as long as you copy it, but a method that takes the key/value and puts it into the map would be my preference.
If you must return the map you should return a read-only version or a copy of it. A set method should also copy the map.
It is a bad idea to allow callers to mutate the data inside of a class without the class knowing, passing or holding onto mutable data is a bad idea.
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