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javasyntaxoperatorsjava-8

Why was the double colon operator chosen for Java 8?

Prior to Java 8, my observation was that the de facto standard for referring to member methods was by using the # symbol (such as Object#toString()). Then along came Java 8 which instead chose the :: operator for method references for seemingly no reason.

Has there been an official explanation or justification for why :: in particular was chosen?

Solution

  • You could find an "official explanation or justification" from Brian Goetz. You should read the complete discussion but this is an extract :

    The :: infix syntax:

       ClassName::methodName 
   ClassName<T>::methodName 
   ClassName::<U>genericMethodName

    works acceptably well. Some people like it, and some people hate it -- just like #. There's never going to be a perfect syntax for anything that makes everyone jump up in unison and say "yeah, that's it!" But :: is OK, and using up :: here is far better than using up #. (And, while this might look a little weird to C++ programmers, the overlap between the Java and C++ developer bases at this point is small enough that I don't think we should be too worried about that.)