Weird java.lang.InstantiationException and java.lang.NoSuchMethodException after upgrading from JDK8 to JDK11

Question

I have the following code which builds and works fine under JDK8:

@FunctionalInterface
public interface ThrowingFunction<T, R, E extends Throwable> {
    R apply(T t) throws E;

    static <T, R, E extends Throwable> Function<T, R> unchecked (ThrowingFunction<T, R, E> function) {
        return t -> {
            try {
                return function.apply(t);
            }
            catch (Throwable e) {
                throw new RuntimeException(e);
            }
        };
    }
}

And:

@Component
public class CronJobDuplicationCheckStrategiesRegistry {

    private final Map<String, Set<CronJobDuplicationCheckStrategy>> duplicationStrategies;

    CronJobDuplicationCheckStrategiesRegistry(final CronJobsRegistry cronJobsRegistry) {
        duplicationStrategies = cronJobsRegistry.get()
            .stream()
            .collect(Collectors.toMap(
                clazz -> clazz.getName(),
                ThrowingFunction.unchecked(
                    clazz -> clazz.getDeclaredConstructor()
                                  .newInstance()
                                  .getDuplicationStrategies())));
    }

    public Set<CronJobDuplicationCheckStrategy> get(String jobClass) {
        return duplicationStrategies.get(jobClass);
    }
}

This code fails to compile under JDK11 with the following error:

[ERROR] Failed to execute goal org.apache.maven.plugins:maven-compiler-plugin:3.3:compile (default-compile) on project cron-api: Compilation failure: Compilation failure: 
[ERROR] /java/org/foo/src/main/java/org/foo/jobs/CronJobDuplicationCheckStrategiesRegistry.java:[26,120] unreported exception java.lang.NoSuchMethodException; must be caught or declared to be thrown
[ERROR] /java/org/foo/src/main/java/org/foo/src/main/java/org/foo/cron/jobs/CronJobDuplicationCheckStrategiesRegistry.java:[27,109] unreported exception java.lang.InstantiationException; must be caught or declared to be thrown

Could somebody please explain what it's unhappy about and how to fix it?

Answer 1

Could somebody please explain what it's unhappy about and how to fix it?

Replace the E generic type with the actual Throwable:

@FunctionalInterface
public interface ThrowingFunction<T, R> {
    R apply(T t) throws Throwable;

    static <T, R> Function<T, R> unchecked(ThrowingFunction<T, R> function) {
        return t -> {
            try {
                return function.apply(t);
            } catch (Throwable e) {
                throw new RuntimeException(e);
            }
        };
    }
}

... the following code which builds and works fine under JDK8

I believe the issue originates in the catching mechanism that is not somehow compatible with the E generic type and is related to the statement at JLS 8.1.2. Generic Classes and Type Parameters:

It is a compile-time error if a generic class is a direct or indirect subclass of Throwable (§11.1.1).

This restriction is needed since the catch mechanism of the Java Virtual Machine works only with non-generic classes.

Frankly, it's a guess and I have no idea why is this is reproducible with JDK 11 but not JDK 8 - that's very strange.

I hope I helped you at least fix the issue.