Android Studio compile project with Java 8?

When goes to JDK setting you can:

add in "android app" module build.gradle

compileOptions {
    sourceCompatibility JavaVersion.VERSION_1_8
    targetCompatibility JavaVersion.VERSION_1_8
}

setup sdk path in gradle.properties

org.gradle.java.home=/path_to_java_sdk_8/jdk1.8

check also .idea/modules/compiler.xml against 1.7/1.8

<?xml version="1.0" encoding="UTF-8"?>
<project version="4">
  <component name="CompilerConfiguration">
      ...
    <bytecodeTargetLevel target="1.8">
      <module name="app" target="1.7" />
    </bytecodeTargetLevel>
  </component>

and misc.xml

<?xml version="1.0" encoding="UTF-8"?>
  <project version="4">
    ....
   <component name="ProjectRootManager" version="2" languageLevel="JDK_1_7" 
              default="false" assert-keyword="true" 
              jdk-15="true" project-jdk-name="1.8" project-jdk-type="JavaSDK">
     <output url="file://$PROJECT_DIR$/build/classes" />
  </component>
  <component name="ProjectType">
    <option name="id" value="Android" />
  </component>
 </project>

BTW: if you want compile againsta java 1.8 you need to uae "jack" see https://source.android.com/source/jack.html