gradlew error help pls

Downloaded 1.12.2 forge mdk v14.23.5.2847, created a folder into it, unpacked the archive, entered "gradlew genEclipseRuns" into the command line, entered eclipse and made a Gradle Project, fixed all errors. But there was one left:

WARNING: An illegal reflective access operation has occurred
WARNING: Illegal reflective access by GradleStart (file:/C:/Users/USER/.gradle/caches/minecraft/net/minecraftforge/forge/1.12.2-14.23.5.2847/start/) to field java.lang.ClassLoader.sys_paths
WARNING: Please consider reporting this to the maintainers of GradleStart
WARNING: Use --illegal-access=warn to enable warnings of further illegal reflective access operations
WARNING: All illegal access operations will be denied in a future release
[15:36:17] [main/INFO] [GradleStart]: Extra: []
Exception in thread "main" java.lang.ClassCastException: class jdk.internal.loader.ClassLoaders$AppClassLoader cannot be cast to class java.net.URLClassLoader (jdk.internal.loader.ClassLoaders$AppClassLoader and java.net.URLClassLoader are in module java.base of loader 'bootstrap')
    at net.minecraftforge.gradle.GradleForgeHacks.searchCoremods(GradleForgeHacks.java:85)
    at net.minecraftforge.gradle.GradleStartCommon.launch(GradleStartCommon.java:86)
    at GradleStart.main(GradleStart.java:25)