Error:(3, 20) java: package jdk.internal.misc is not visible
(package jdk.internal.misc is declared in module java.base, which does
not export it to module com.jigsaw.npe)

package experiment;
import jdk.internal.misc.Unsafe;

public class CompareAndSwap {

    static Unsafe UNSAFE = Unsafe.getUnsafe();
    ...
}

module com.jigsaw.npe {
    requires java.base;
}