Gradle 3.5 released : androiddev
./gradlew wrapper --gradle-version 3.5 --distribution-type all
ちなみに以下を書き換える方法については
distributionUrl=https\://services.gradle.org/distributions/gradle-3.5-all.zip
Jake がコメント.
That's mostly fine, but it doesn't update the bootstrap script nor the bootstrap jar. Basically you just miss out on improvements to those two components which can help with things like OS compatibility and caching of the Gradle runtime.
コマンドラインから更新したほうが良さそうです.
