Found java version null. Please Help

I was just trying to install forge 1.15.2 MDK (https://files.minecraftforge.net/maven/net/minecraftforge/forge/index_1.15.2.html [Recommended Edition])

When I entered “gradlew eclipse” in cmd and pressed enter it gave me an error.

FAILURE: Build failed with an exception.

• Where:
  Build file ‘C:\Users\david\Desktop\Minecraft Modding\TestMod\build.gradle’ line: 11

• What went wrong:
  A problem occurred evaluating root project ‘TestMod’.

Failed to apply plugin [id ‘net.minecraftforge.gradle’]
Found java version null. Minimum required is 1.8.0_101. Versions 11.0.0 and newer are not supported yet.

• Try:
  Run with --stacktrace option to get the stack trace. Run with --info or --debug option to get more log output. Run with --scan to get full insights.

• Get more help at https://help.gradle.org

BUILD FAILED in 4s