java - Why should a tag interface appear last in a generic class declaration? -


this extract core java(volume 1,by cay s. hortsman). here have

class interval<t extends  comparable & serializable>

as goes as:" note:you may wonder happens if switch bounds:

class interval<t extends serializable & comparable>

in case, raw type replaces t serializable, , compiler inserts casts comparable when necessary. for efficiency, should therefore put tagging interfaces (that is, interfaces without methods) @ end of bounds list. " have no idea why tagging interface efficiency , wish plain answer.

assuming mr. horstmann says still true, there slight efficiency difference.

everywhere refer instance comparable (i.e. invoke 1 of methods) compiler has insert runtime type check (i.e. cast) verify object indeed comparable. putting tag interface last lets compiler check proper type @ compile time , omit casts.

but you'd never notice difference in execution speed.


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