Example case for how URLClassLoader breaks the JarFile cache

BrokenURLClassLoader.java

import java.net.*;
import java.util.List;
import java.util.stream.Collectors;
import java.util.stream.IntStream;

/**
 * To run, first create a jar file:
 *
 * $ touch blah.txt
 * $ jar cf blah.jar blah.txt
 * $ rm blah.txt
 */
public class BrokenURLClassLoader {

    public static final int PARALLEL = 10;

    public static void main(String[] args) throws Throwable {
        URL[] urls = {new URL("jar:file:blah.jar!/")};
        String filename = "blah.txt";

        for (int iter = 0; ; iter++) {
            List<Throwable> failures = IntStream.rangeClosed(1, PARALLEL)
                    .parallel()
                    .mapToObj(i -> {
                        try {
                            URLClassLoader urlc = new URLClassLoader(urls);
                            urlc.getResourceAsStream(filename).close();
                            urlc.close();
                        } catch (Throwable t) {
                            return t;
                        }
                        return null;
                    })
                    .filter(t -> t != null)
                    .collect(Collectors.toList());

            if (failures.size() != 0) {
                System.err.println("failures on iteration " + iter);

                failures.forEach(t -> t.printStackTrace());

                System.exit(1);
            }
        }

    }
}