CleanerDemo.java

// run with java -showversion CleanerDemo in Java 16 and 17 to see different results
import java.lang.ref.*;

public class CleanerDemo {
    public static void main(String... args) throws InterruptedException {
        Cleaner cleaner = Cleaner.create();
        Cleaner.Cleanable cleanable = cleaner.register(new Object(),
                () -> System.out.println("My cleaner thread priority is " +
                        Thread.currentThread().getPriority()));
        System.gc();
        Thread.sleep(1000);
    }
}