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Java Forum / General / October 2006'break' statements to jump among switch cases: how to?
Hi all Is there a legal way to use break statements to jump from one switch case to another (see below)? Thanks! switch(mode) { case Partial: if(reader == null) break Full; ... break; case Full: ... break; } No. The break lable; jump is restricted to loops AFAIK. > No. > > The break lable; jump is restricted to loops AFAIK. If it works this way, I think that the Java switch statement flow is unconsistent, because of the fall-through behavior (that is nothing but a degenerate, implicit jump to a subsequent case statement!). IMHO, fall-through is too much limitative: adding break-to-labeled-statement statements to the switch syntax would be a useful and elegant extension to the current simple break statement (the same purpose of the ugly-but-effective 'go to' statement of C#). To be used wisely and sparingly, obviously! > If it works this way, I think that the Java switch statement flow is > unconsistent, because of the fall-through behavior (that is nothing but > a degenerate, implicit jump to a subsequent case statement!). No it is consistent - You are guaranteed that a switch statement will execute from top-to-bottom and fallthrough will occur untill the switch ends (either by reaching the end of the switch or until a break statement is executed). > IMHO, fall-through is too much limitative: adding > break-to-labeled-statement statements to the switch syntax would be a > useful and elegant extension to the current simple break statement (the > same purpose of the ugly-but-effective 'go to' statement of C#). This is very much like the 'goto' which IMHO is an ingredient for spagetti code > To be used wisely and sparingly, obviously! famous last words > This is very much like the 'goto' which IMHO is an ingredient for > spagetti code And hence why C# has it :) (There you need to end every case block with either a break or a "goto case label", there is no fallthrough.) > Is there a legal way to use break statements to jump from one switch > case to another (see below)? [quoted text clipped - 13 lines] > break; > } The only way I know is: run from one case into the next case by *not* doing a "break". The code below does what you wanted in your code above. switch(mode) { case Partial: if(reader != null) { ... break; } /*FALL THROUGH*/ case Full: ... break; } But you should do such things only when absolutely needed. At least put a fat comment there, stating that you omitted the "break" on purpose and not by accident.  SignatureThomas >> Is there a legal way to use break statements to jump from one switch >> case to another (see below)? [quoted text clipped - 34 lines] > a fat comment there, stating that you omitted the "break" on purpose and > not by accident. Thanks, Thomas. I wrote the following post to Chris just before reading your comment: "If it works this way, I think that the Java switch statement flow is unconsistent, because of the fall-through behavior (that is nothing but a degenerate, implicit jump to a subsequent case statement!). IMHO, fall-through is too much limitative: adding break-to-labeled-statement statements to the switch syntax would be a useful and elegant extension to the current simple break statement (the same purpose of the ugly-but-effective 'go to' statement of C#). To be used wisely and sparingly, obviously!" > Hi all > [quoted text clipped - 15 lines] > break; > } Not as arbitrary jumps among cases. See http://www.acm.org/classics/oct95/ for the main arguments against doing it. Possible solutions include running the switch multiple times, changing mode as needed, or putting the common work in a method, called in each situation in which it is needed. Patricia Free MagazinesGet these publications absolutely FREE for up to 12 months. There are no hidden fees and no obligation. Simply choose a title, complete the application form and submit it. Read more ...
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