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    1+: Since it screws up mocking; consider creating interfaces or abstract classes for each "final" class.
    – Spoike
    Commented Jul 14, 2011 at 11:49
  • 1
    You can consider the Java API itself and how often you will find the usage of the 'final' keyword. In fact, it is not used very often. It is used in cases were performance might get bad due to the dynamic binding taking place when "virtual" methods are called (in Java all methods are virtual if they are not declared as 'final' or 'private'), or when introducing custom subclasses of a Java API class might arise consistency issues, such as subclassing 'java.lang.String'. A Java String is a value object per definition and must not change its value later on. A subclass could break this rule.
    – Jonny Dee
    Commented Jul 16, 2011 at 20:46
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    @Jonny Most of the Java API is badly designed. Remember that the bulk of it is more than ten years old and many best practices have been developed in the meantime. But don’t take my word for it: the Java engineers themselves say so, first and foremost Josh Bloch who has written in detail about this, e.g. in Effective Java. Rest assured that if the Java API were developed today, it would look very different, and final would play a much bigger role.
    – Konrad Rudolph
    Commented Jul 17, 2011 at 10:07
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    I'm still not convinced that using 'final' more often has become a best practice. In my opinion, the 'final' should really be used only if performance requirements dictate it, or if you must assure consistency cannot be broken by subclasses. In all other cases necessary documentation should go into, well, the documentation (which needs to be written anyway), and not into the source code as keywords that enforce certain usage patterns. To me, that's kind of playing god. Using annotations whould be a better solution. One could add a '@final' annotation and the compiler could issue a warning.
    – Jonny Dee
    Commented Jul 17, 2011 at 17:47
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    "Jon Skeet" link is dead. Probably it was moved to this SO question.
    – Alexander Malakhov
    Commented Aug 18, 2016 at 5:49