title: Do I need to upgrade to Java 8 for my Android Studio if I'm just writing in Kotlin?
body: <p>I'm working on an old project, which uses Java. It is based on Java 7. 
  But it's now all Kotlin classes for new code.</p>
  
  <p>In our gradle it is still</p>
  
  <pre><code>compileOptions {
      sourceCompatibility JavaVersion.VERSION_1_7
      targetCompatibility JavaVersion.VERSION_1_7
  }
  </code></pre>
  
  <p>Just curious, is there a need to upgrade to Java 8, if moving forward I'll be writing in Kotlin?</p>
  
  <pre><code>compileOptions {
      sourceCompatibility JavaVersion.VERSION_1_8
      targetCompatibility JavaVersion.VERSION_1_8
  }
  </code></pre>
  
  <p>From <a href="https://developer.android.com/studio/write/java8-support" rel="noreferrer">https://developer.android.com/studio/write/java8-support</a>, it looks like the only reason to do the above is if we intend to write in Java 8. But I'm curious and want to avoid not upgrading and missing out some neat new Java optimization that could benefit to Kotlin project in Android?</p>