Require and use JDK 8 in all artifacts.

Author: greenrobot-team

objectbox-java-api/build.gradle

@@ -3,7 +3,8 @@ apply plugin: 'java'
 group = 'io.objectbox'
 version= rootProject.version
 
-sourceCompatibility = 1.7
+sourceCompatibility = JavaVersion.VERSION_1_8
+targetCompatibility = JavaVersion.VERSION_1_8
 
 task javadocJar(type: Jar, dependsOn: javadoc) {
     classifier = 'javadoc'

objectbox-java/build.gradle

@@ -4,7 +4,8 @@ apply plugin: 'findbugs'
 group = 'io.objectbox'
 version= rootProject.version
 
-sourceCompatibility = '1.7'
+sourceCompatibility = JavaVersion.VERSION_1_8
+targetCompatibility = JavaVersion.VERSION_1_8
 
 tasks.withType(FindBugs) {
     reports {

objectbox-kotlin/build.gradle

@@ -20,7 +20,8 @@ buildscript {
 apply plugin: 'kotlin'
 apply plugin: 'org.jetbrains.dokka'
 
-sourceCompatibility = 1.7
+sourceCompatibility = JavaVersion.VERSION_1_8
+targetCompatibility = JavaVersion.VERSION_1_8
 
 dokka {
     outputFormat = 'html'

objectbox-rxjava/build.gradle

@@ -3,7 +3,8 @@ apply plugin: 'java'
 group = 'io.objectbox'
 version= rootProject.version
 
-sourceCompatibility = 1.7
+sourceCompatibility = JavaVersion.VERSION_1_8
+targetCompatibility = JavaVersion.VERSION_1_8
 
 dependencies {
     compile project(':objectbox-java')

tests/objectbox-java-test/build.gradle

@@ -2,8 +2,8 @@ apply plugin: 'java'
 
 uploadArchives.enabled = false
 
-targetCompatibility = '1.8'
-sourceCompatibility = '1.8'
+sourceCompatibility = JavaVersion.VERSION_1_8
+targetCompatibility = JavaVersion.VERSION_1_8
 
 repositories {
     // Native lib might be deployed only in internal repo

tests/test-proguard/build.gradle

@@ -2,8 +2,8 @@ apply plugin: 'java'
 
 uploadArchives.enabled = false
 
-sourceCompatibility = 1.7
-targetCompatibility = 1.7
+sourceCompatibility = JavaVersion.VERSION_1_8
+targetCompatibility = JavaVersion.VERSION_1_8
 
 repositories {
     // Native lib might be deployed only in internal repo