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I have an List<TestBuilder> testBuilders; Test has a function build of type Test

I did testBuilders.stream().map(Test::build()).collect()

I want to collect above in array of Test i.e Test[]

I am not sure what would go in collect function

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  • Not really related but: are you sure you want to have list of test builders? Should one builder produce only one test, or one builder should produce N tests? If one builder should generate N tests you could use code like Stream.generate(someSingleTestBuilder::build).limit(N).toArray(Test[]::new); Commented Apr 30, 2019 at 18:59
  • 1
    Possibly related: Java 8 fill array with supplier Commented Apr 30, 2019 at 19:02

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Use the terminal operation Stream::toArray which packs the sequence of items into an array. However, you have to define a provided generator IntFunction<A[]> to allocate the type of returned array:

Test[] array = testBuilders.stream().map(Test::build).toArray(size -> new Test[size]);

The lambda expression size -> new Test[size] should be replaced with a method reference:

Test[] array = testBuilders.stream().map(Test::build).toArray(Test[]::new);
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You can use 

whatever.stream().toArray(WhatEverClass[]::new);

to create an array for objects of type WhatEverClass based on "whatever" stream of objects of that type. Thus: no need to collect() anything.

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