If I have the following statement within a class where Synapse
is an abstract type:
private final List<Synapse> synapses;
Does final
allow me to still be able to change the state of the Synapse
objects in the List
, but prevent me from adding new Synapse
objects to the list? If I am wrong, could you please explain what final
is doing and when I should be using the keyword final
instead.
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Answer
No, the final keyword does not make the list, or its contents immutable. If you want an immutable List, you should use:
List<Synapse> unmodifiableList = Collections.unmodifiableList(synapses);
What the final keyword does is prevent you from assigning a new value to the ‘synapses’ variable. I.e., you cannot write:
final List<Synapse> synapses = createList(); synapses = createNewList();
You can, however, write:
List<Synapse> synapses = createList(); synapses = createNewList();
In essense, you can still change, add and remove the contents of the list, but cannot create a new list assigned to the variable synapses.