restriction - When to restrict a class from extending a class? -
is there point in programmer's lifetime restrict class extending class? example don't want package
extend box
.
yes. in java call final
class. in c# call sealed
class.
it done because cannot predict many ways consumer might extend class, prevent having design class account possible ways might extend it, seal , require consumer use composition instead of inheritance.
further reading
why many of framework classes sealed?
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