upgrade version

build.gradle

@@ -2,7 +2,8 @@ plugins {
     id 'java'
     id 'idea'
 }
-
+sourceCompatibility = JavaVersion.VERSION_1_8
+targetCompatibility = JavaVersion.VERSION_1_8
 tasks.withType(JavaCompile) {
     options.compilerArgs << '-Xlint:none'
     options.compilerArgs << '-Xlint:deprecation' << "-Werror"
@@ -15,6 +16,5 @@ project(':backend') {
     group = "org.bdware.sc.example"
     repositories {
         mavenCentral()
-        maven { url 'https://maven.aliyun.com/repository/public' }
     }
 }