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Editorial Team
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Asked: 2026-05-24T04:29:57+00:00

Will first line work faster than second line in GWT? Is there difference of

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Will first line work faster than second line in GWT? Is there difference of translation this code in JavaScript in different GWT versions? 

ArrayList<String> list = new ArrayList<String>(); 

List<String> list = new ArrayList<String>();

As i know if i will write declearet type List, JavaScript performance will be worst, because will check is this List LinkedList or ArrayList or other type of list. Is it right?

Will it improve performance if i will write

ArrayList<String> list = new ArrayList<String>();

instead of 

List<String> list = new ArrayList<String>();

?

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1 Answer

  1. Editorial Team

    Both lines are equivalent. The GWT compiler performs an optimization called “type tightening.” You can watch how the compiler optimizes a particular method by defining a Java environment property when you compile a module:

    -Dgwt.jjs.traceMethods=Hello.onModuleLoad:OtherClass.otherMethod

    From the JProgram source:

    The format to trace methods is a colon-separated list of “className.methodName”, such as “Hello.onModuleLoad:Foo.bar”. You can fully-qualify a class to disambiguate classes, and you can also append the JSNI signature of the method to disambiguate overloads, “Foo.bar(IZ)”.

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