String concatenation with Groovy

Question

What is the best  idiomatic  way to concatenate Strings in Groovy   Option 1   calculateAccountNumber bank  branch  checkDigit  account        bank   branch   checkDigit   account     Option 2   calculateAccountNumber bank  branch  checkDigit  account          bank branch checkDigit account      I ve founded an interesting point about this topic in the old Groovy website  Things you can do but better leave undone      As in Java  you can concatenate Strings with the     symbol  But Java   only needs that one of the two items of a     expression to be a   String  no matter if it s in the first place or in the last one  Java   will use the toString   method in the non-String object of your       expression  But in Groovy  you just should be safe the first item of   your     expression implements the plus   method in the right way    because Groovy will search and use it  In Groovy GDK  only the Number   and String StringBuffer Character classes have the plus   method   implemented to concatenate strings  To avoid surprises  always use   GStrings

User · Answer

Reproducing tim yates answer on current hardware and adding leftShift   and concat   method to check the finding      String leftShift        foo  lt  lt  bar  lt  lt  baz        String concat        foo concat bar          concat baz          toString         The outcome shows concat   to be the faster solution for a pure String  but if you can handle GString somewhere else  GString template is still ahead  while honorable mention should go to leftShift    bitwise operator  and StringBuffer   with initial allocation   Environment               Groovy  2 4 8   JVM  OpenJDK 64-Bit Server VM  25 191-b12  Oracle Corporation        JRE  1 8 0 191       Total Memory  238 MB       Maximum Memory  3504 MB   OS  Linux  4 19 13-300 fc29 x86 64  amd64   Options           Warm Up  Auto  - 60 sec    CPU Time Measurement  On                                      user  system  cpu  real  String adder                         453       7  460   469 String leftShift                     287       2  289   295 String concat                        169       1  170   173 GString template                      24       0   24    24 Readable GString template             32       0   32    32 GString template toString            400       0  400   406 Readable GString template toString   412       0  412   419 StringBuilder                        325       3  328   334 StringBuffer                         390       1  391   398 StringBuffer with Allocation         259       1  260   265

User · Answer

I always go for the second method  using the GString template   though when there are more than a couple of parameters like you have  I tend to wrap them in   X  as I find it makes it more readable   Running some benchmarks  using Nagai Masato s excellent GBench module  on these methods also shows templating is faster than the other methods    Grab   com googlecode gbench gbench 0 3 0-groovy-2 0    import gbench    def  foo bar baz       foo    bar    baz    new BenchmarkBuilder   run  measureCpuTime false          Just add the strings    String adder        foo   bar   baz          Templating    GString template          foo bar baz           I find this more readable    Readable GString template           foo   bar   baz            StringBuilder    StringBuilder        new StringBuilder   append  foo                           append  bar                           append  baz                           toString          StringBuffer        new StringBuffer   append  foo                          append  bar                          append  baz                          toString         prettyPrint     That gives me the following output on my machine   Environment               Groovy  2 0 0   JVM  Java HotSpot TM  64-Bit Server VM  20 6-b01-415  Apple Inc         JRE  1 6 0 31       Total Memory  81 0625 MB       Maximum Memory  123 9375 MB   OS  Mac OS X  10 6 8  x86 64    Options           Warm Up  Auto    CPU Time Measurement  Off  String adder               539 GString template           245 Readable GString template  244 StringBuilder              318 StringBuffer               370   So with readability and speed in it s favour  I d recommend templating  -   NB   If you add toString   to the end of the GString methods to make the output type the same as the other metrics  and make it a fairer test  StringBuilder and StringBuffer beat the GString methods for speed   However as GString can be used in place of String for most things  you just need to exercise caution with Map keys and SQL statements   it can mostly be left without this final conversion  Adding these tests  as it has been asked in the comments      GString template toString          foo bar baz  toString          Readable GString template toString           foo   bar   baz   toString         Now we get the results   String adder                        514 GString template                    267 Readable GString template           269 GString template toString           478 Readable GString template toString  480 StringBuilder                       321 StringBuffer                        369   So as you can see  as I said   it is slower than StringBuilder or StringBuffer  but still a bit faster than adding Strings     But still lots more readable   Edit after comment by ruralcoder below  Updated to latest gbench  larger strings for concatenation and a test with a StringBuilder initialised to a good size    Grab   org gperfutils gbench 0 4 2-groovy-2 1     def  foo bar baz       foo    50   bar    50   baz    50   benchmark        Just add the strings    String adder        foo   bar   baz          Templating    GString template          foo bar baz           I find this more readable    Readable GString template           foo   bar   baz          GString template toString          foo bar baz  toString          Readable GString template toString           foo   bar   baz   toString            StringBuilder    StringBuilder        new StringBuilder   append  foo                           append  bar                           append  baz                           toString          StringBuffer        new StringBuffer   append  foo                          append  bar                          append  baz                          toString          StringBuffer with Allocation        new StringBuffer  512   append  foo                          append  bar                          append  baz                          toString         prettyPrint     gives  Environment               Groovy  2 1 6   JVM  Java HotSpot TM  64-Bit Server VM  23 21-b01  Oracle Corporation        JRE  1 7 0 21       Total Memory  467 375 MB       Maximum Memory  1077 375 MB   OS  Mac OS X  10 8 4  x86 64   Options           Warm Up  Auto  - 60 sec    CPU Time Measurement  On                                      user  system  cpu  real  String adder                         630       0  630   647 GString template                      29       0   29    31 Readable GString template             32       0   32    33 GString template toString            429       0  429   443 Readable GString template toString   428       1  429   441 StringBuilder                        383       1  384   396 StringBuffer                         395       1  396   409 StringBuffer with Allocation         277       0  277   286

User · Answer

def my string    some string  println  here      my string    Not quite sure why the answer above needs to go into benchmarks  string buffers  tests  etc

[string] String concatenation with Groovy

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