Home/ Questions/Q 7641081
In Process

The Archive Base Latest Questions

Editorial Team
  • 0
Asked: 2026-05-31T08:50:03+00:00

I tend to use (or even overuse) double braces object intialization in GWT. For

  • 0

I tend to use (or even overuse) double braces object intialization in GWT. For me it looks more readable and more declarative.

new FastMap<Object>(){{
    put("Value", 12);
    put("Unit", "Kg");
}};

Before today I was not aware that this syntax is not just instantiate object but also create AnonymousInnerClass for it. Now I am concerned how GWT deal with them.

  1. How this syntax affects perfomance of the execution?
  2. How this syntax affects compiled size?
  3. Any other bad thing?

I have thousands of such initializations in my app.

Share

Leave an answer

You must login to add an answer.

Need An Account,

1 Answer

  1. Editorial Team

    My findings. Test code. I am creating single list with 4 maps with 21 item each. I am measuring size of all generated JavaScript files. Results:

    Empty (just empty code to make sure that GWT support code rendered):

    • PRETTY = 533 KB (546 602 bytes)
    • OBF = 212 KB (217 601 bytes)
    • Number of new = 167

    Code without double braces:

    • PRETTY = 557 KB (570 682 bytes)
    • OBF = 222 KB (227 663 bytes)
    • Number of new = 171

    And same code with double braces:

    • PRETTY = 567 KB (581 004 bytes)
    • OBF = 228 KB (234 089 bytes)
    • Number of new = 177

    I think results are pretty self-explanatory.

    • 0