AndroidStudio 3.0: Java 8 stream not compile (Call requires API level 24)

Question

Java 8, and I install new Android Studio 3.0.

Add code:

 List<String> myList =   Arrays.asList("a1", "a2", "b1", "c2", "c1");

        myList
                .stream()
                .filter(s -> s.startsWith("c"))
                .map(String::toUpperCase)
                .sorted()
                .forEach(System.out::println);

But I get compile error:

Call requires API level 24 (current min is 15) java.util.stream.Collection

Answer 1

While there is a bunch of Java 1.8 support in Android Studio 3.0 (lambdas, method references, default interface methods), not all of 1.8 is supported for all Android APIs. In particular, java.util.stream is not supported until API 24.

See the developer docs: https://developer.android.com/studio/write/java8-support.html#supported_features

A good library to get backported Java 1.8 libraries such as java.util.stream is StreamSupport: https://github.com/streamsupport/streamsupport

Answer 2

In order to use Streams and other java 8 API without requiring minimum API level 24, you need to do the following:

• Upgrade Android Gradle Plugin to 4.0.0 or higher

  classpath 'com.android.tools.build:gradle:4.0.0
  

• Then add this dependency to your build.gradle file:

  dependencies { 
  
     coreLibraryDesugaring 'com.android.tools:desugar_jdk_libs:1.0.6'
  
     ....
  }
  

• Finally Add this to your build.gradle file:

  compileOptions {
  
      // Flag to enable support for new language APIs
      coreLibraryDesugaringEnabled true
  
      targetCompatibility JavaVersion.VERSION_1_8
      sourceCompatibility JavaVersion.VERSION_1_8
  }
  

Enjoy Java 8 Streams and Time APIs :)