Lambdas on Android...its a brave new world. See: https://github.com/evant/gradle-retrolambda

README.md

README

Limitations

• Any limitations documented https://github.com/evant/gradle-retrolambda and https://github.com/orfjackal/retrolambda
• This only adds language support for lambda; not API support (ex: collection streams).

build.gradle

// Uninteresting parts removed for clarity
buildscript {
    repositories {
        mavenCentral()
    }

    dependencies {
        classpath 'me.tatarka:gradle-retrolambda:2.2.3'
    }
}

repositories {
    mavenCentral()
}

apply plugin: 'com.android.application'
apply plugin: 'retrolambda'

android {
    compileOptions {
        sourceCompatibility JavaVersion.VERSION_1_8
        targetCompatibility JavaVersion.VERSION_1_8
    }
}

MyActivity.java

public class MyActivity extends Activity {
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_my);

        // Old school
        Button button = (Button) findViewById(R.id.button);
        button.setOnClickListener(new OnClickListener() {
            @Override
            public void onClick(View v) {
                Toast.makeText(MyActivity.this, "Hello", Toast.LENGTH_SHORT).show();
            }
        });

        // Verbose lambda expression
        button.setOnClickListener((View) -> {
            Toast.makeText(this, "Hello", Toast.LENGTH_SHORT).show();
        });

        // Terse lambda expression
        button.setOnClickListener((View) -> Toast.makeText(this, "Hello", Toast.LENGTH_SHORT).show());

        // Method references
        button.setOnClickListener(this::handleButtonClick);
    }

    private void handleButtonClick(View view) {
        Toast.makeText(this, "Hello", Toast.LENGTH_SHORT).show();
    }
}