Building a Java project and running Gradle both require the installation of a JDK.
Most Gradle users conveniently use the Java installation that is running Gradle to build and test their application.

Gradle Blog

Gradle 6.7 introduces Java toolchain support, allowing developers to declare a single Java version for their entire project build. Gradle automatically detects installed JDKs or downloads the required version from AdoptOpenJDK if not found. This eliminates the need to manually configure individual tasks like compilation, testing, and javadoc separately. Task-level overrides are also supported for scenarios requiring multiple Java versions. The feature also enables building with unreleased Java versions and improves build cache consistency across machines.

Introducing Java toolchains