How to use lambda expression in android

Its because maybe you are using Java 7 and Actually, Retrolambda is a library which we can use with Java 8 lambda expressions.

So How To SetUp :-

Add this following to your project’s main build.gradle

 classpath 'me.tatarka:gradle-retrolambda:3.2.3'

then add this to your application module’s build.gradle

apply plugin: 'me.tatarka.retrolambda'

then we need to add these lines to your application module’s build.gradle

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

and done, you can use it like below :-

eg.) Clicking a button with Retrolambda.

  // RETROLAMBDA WAY
        clickMeBtn.setOnClickListener(view ->
                Toast.makeText(MainActivity.this,
             "This is the way to click a button to make a toast with RetroLambda !", Toast.LENGTH_LONG).show());

Anonymous class new View.OnClickListener() can be replaced with lambda .

Add the below code to your app level gradle:

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

android {
compileSdkVersion 29
buildToolsVersion "29.0.2"

defaultConfig {
    applicationId "com.sanjay.sanjay"
    minSdkVersion 15
    targetSdkVersion 29
    versionCode 1
    versionName "1.0"

    testInstrumentationRunner "androidx.test.runner.AndroidJUnitRunner"
}

buildTypes {
    release {
        minifyEnabled false
        proguardFiles getDefaultProguardFile('proguard-android-optimize.txt'), 'proguard-rules.pro'
    }
}
compileOptions {
    sourceCompatibility JavaVersion.VERSION_1_8
    targetCompatibility JavaVersion.VERSION_1_8
}

}

add like this in you app.gradle file in android studio