A sample RxJava-Android and retrolambda gradle configuration for Android Studio on Mac OS.

build.gradle

apply plugin: 'com.android.application'

android {
    compileSdkVersion 22
    buildToolsVersion "22.0.1"

    defaultConfig {
        applicationId "com.example.databaseexample"
        minSdkVersion 14
        targetSdkVersion 22
        versionCode 1
        versionName "1.0"
        testInstrumentationRunner "android.support.test.runner.AndroidJUnitRunner"
    }
    buildTypes {
        release {
            minifyEnabled false
            proguardFiles getDefaultProguardFile('proguard-android.txt'), 'proguard-rules.pro'
        }
    }

    packagingOptions {
        exclude 'LICENSE'
        exclude 'LICENSE.txt'
    }

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

buildscript {
    repositories {
        mavenCentral()
    }

    dependencies {
        classpath 'me.tatarka:gradle-retrolambda:3.0.1'
    }
}

repositories {
    mavenCentral()
}

apply plugin: 'me.tatarka.retrolambda'

retrolambda {
    jdk '/Library/Java/JavaVirtualMachines/jdk1.8.0_45.jdk/Contents/Home'//System.getenv("JAVA_8")
    oldJdk System.getenv("JAVA_HOME")
    javaVersion JavaVersion.VERSION_1_7
}

dependencies {
    compile fileTree(dir: 'libs', include: ['*.jar'])
    compile 'com.android.support:appcompat-v7:22.1.0'

    compile 'io.reactivex:rxandroid:0.24.0'
    
    // other dependencies (not relevant to this example)
    
    compile 'com.squareup.picasso:picasso:2.5.2'
    compile 'com.squareup.retrofit:retrofit:1.9.0'
    compile 'com.google.code.gson:gson:2.3'

    androidTestCompile 'com.android.support.test:runner:0.2'
    androidTestCompile 'com.android.support.test:rules:0.2'
    androidTestCompile 'org.assertj:assertj-core:1.7.1'
    androidTestCompile 'com.squareup.assertj:assertj-android:1.0.0'
    androidTestCompile 'com.android.support.test.espresso:espresso-core:2.1'
    androidTestCompile 'com.android.support:support-annotations:22.1.0'

    testCompile 'junit:junit:4.12'
    testCompile 'com.android.support.test:runner:0.2'
    testCompile 'com.android.support.test:rules:0.2'
    testCompile 'org.assertj:assertj-core:1.7.1'
    testCompile 'com.android.support:support-annotations:22.1.0'
}