This answer gives an indication that class String
is declared final
for thread safety, which does not convince.
This answer does not convince when it says: And so, you make the classes final. There can be no mutable String, because its an immutable class and its final.
Because,
below field with final
modifier,
/** The value is used for character storage. */
private final char value[];
in class String
would suffice/indicate that data stored in the created object is suppose to be immutable and thread safe.
So, class String
being final
has nothing to do with immutability or thread safety.
But it is not clear, why class String
is declared final
?
Because, as per below class definition, it has final
modifier:
public final class String
implements java.io.Serializable, Comparable<String>, CharSequence
{ .... }
So, class String
cannot be inherited.
Despite field value[]
in class String
is declared final
, additionaly, What is the necessity for class String
also to be final
?
Note: Answers to this question will give an idea behind this design decision
class String
beingfinal
has nothing to do with immutability. But this answer says here:Another reason is thread safety: Immutables are always thread safe
. I think thread safety can be ensured by just making the field ofclass String
asfinal
, but notclass String
asfinal
? 2) Similarly this answer does not make sense to me:And so, you make the ..an immutable class and its final.
String
and he wants to make sure that he knows in before, how its methods are implemented. E.g. he wants to assure that "abc".startsWith("abc") is true and not false because someone has overwritten the method and is not passing aString
but aCustomString
class.