android studio 3.0.1从java jdk1.7升级到1.8版本的时候，出现以下警告：
Warning:The Jack toolchain is deprecated and will not run. To enable support for Java 8 language features built into the plugin, remove 'jackOptions { ... }' from your build.gradle file, and add android.compileOptions.sourceCompatibility 1.8 android.compileOptions.targetCompatibility 1.8 Future versions of the plugin will not support usage of 'jackOptions' in build.gradle. To learn more, go to https://d.android.com/r/tools/java-8-support-message.html
原来build.gradle的配置是这样的 ：
defaultConfig {
jackOptions {
enabled true
}
compileOptions {
sourceCompatibility JavaVersion.VERSION_1_8
targetCompatibility JavaVersion.VERSION_1_8
}
}
只需要删除：
jackOptions {
enabled true
}
即可！
