是否可以在 AndroidAPI < 24上使用 Java8流 API？

我在这里读过这个 邮寄。但是我仍然不能在 minSdkVersion < 24上运行包含 Java8StreamAPI 特性的代码，如下所示。

List<Car> newCars = cars.stream()
.filter(s -> s.getColor().equals("red"))
.collect(Collectors.toList());

由于错误消息，此命令无法运行

调用需要 API 级别24(当前最小值为15) : java.util.Collection # stream

有人知道怎么解决吗？

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最佳答案

[original answer]

You can not use Java8 streams on API level < 24.

However, there are some libraries that backport some of the stream functionality

https://github.com/aNNiMON/Lightweight-Stream-API

https://github.com/konmik/solid

https://sourceforge.net/projects/streamsupport/ (mentioned by @sartorius in comment)

[update k3b 2019-05-23]

https://github.com/retrostreams/android-retrostreams is a spinoff from streamsupport which takes advantage of Android Studio 3.x D8 / desugar toolchain's capability to use interface default & static methods across Jar file boundaries. There are also links to other android-retroXXX ie for CompletableFuture.

[update aeracode 2020-07-24]

Good news, now we can use Java 8 Stream API and more without requiring a minimum API level.

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Since release 8.2 of DexGuard it is possible to use the Java 8 streams API also on Android devices < API level 24. In order to do so, one needs to include the streamsupport library and DexGuard will translate all Java 8 stream API calls to the provided library. No additional handling is needed, and developers can simply code using the provided Java 8 streams API. Dependencies are also translated automatically, so it is possible to use libraries with Java 8 features also for Android development.

This feature will also be included in ProGuard in the near future, stay tuned.

Edit: Proguard 6.1.0 for which there already exists a beta version supports backporting Java 8 stream and time API.

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Create a İnterface. 

public interface Pre<T,R> {
R get(T item);
}

Create a Filter Method.

public static  <T> List<T> Filter(List<T> list, Pre<T,Boolean> pre) {


if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.N)
{
return list.stream().filter(p -> pre.get(p)).collect(Collectors.toList());
}
else
{
List<T> col = new ArrayList<T>();
for (int i = 0 ; i < list.size() ; i++)
if (pre.get(list.get(i)))
col.add(list.get(i));
return col;
}
}

Using Code

    public static class model {
public String Name;
}
List<model> models = new ArrayList<>();
...
List<model> filtermodels = Filter(models,p-> p.Name.equals("filter"));
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Might be a little late to the party, but I just saw that If we use java8.util.stream.StreamSupport then we can run the same functional programming approach and use it prior to Api 24. Eg taken from web3j -

StreamSupport.stream(transactionReceipt.getLogs())
.map(log -> extractEventParameters(event, log))
.filter(Objects::nonNull)
.collect(Collectors.toList());
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Another solution I like to use is to statically use Kotlin's extensions over Collections from Java code, if the project supports both of course:

List<Car> newCars = CollectionsKt.filter(cars, s -> s.getColor().equals("red"));

Same for .map, .reduce, .first, ...etc

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Yes, it is! Starting from AGP 4.0.0 we can use Stream API and some other Java 8+ APIs (e.g. java.time)

Minimal required changes to your app's build.gradle:

android {
compileOptions {
// Flag to enable support for the new language APIs
coreLibraryDesugaringEnabled true
}
}


dependencies {
coreLibraryDesugaring 'com.android.tools:desugar_jdk_libs:1.0.9'
}

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