Following compiles on my platform without any errors.
import java.io.IOException; public class Example { private static final Hello<?> INSTANCE = new Hello<Throwable>() { @Override public void hello() throws Throwable { throw new IOException("hello"); } }; public interface Hello<E extends Throwable> { void hello() throws E; } public static <E extends Throwable> void runHello() throws E { ((Hello<E>) INSTANCE).hello(); } public static void main(String... args) { // NO THROWS DECLARATION runHello(); // THE LINE: Shouldn't this be complained by the compiler? } } But look, the Example#hello method is throwing an IOException, which is a checked exception, from its implementation. And at the same time in the declaration of the main method, it doesn't have any "throws".
As a matter of fact, when I run this, I get a following stack trace.
$ java -cp target/test-classes com.github.dakusui.pcond.ut.providers.Example Exception in thread "main" java.io.IOException: hello at com.github.dakusui.pcond.ut.providers.Example$1.hello(Example.java:9) at com.github.dakusui.pcond.ut.providers.Example.runHello(Example.java:18) at com.github.dakusui.pcond.ut.providers.Example.main(Example.java:23) It is throwing an IOException itself. To me the main method seems to violate its contract (declaration) at runtime, which must not happen.
My questions are
- Why can this program be compiled? Shouldn't it result in a compilation error at THE LINE?
- If it should be compiled for some reason, then why the
mainmethod throws IOException directly. Instead of something else that indicates an undeclared exception (type mismatch) is being thrown?
The detail of my platform is following.
$ java -version openjdk version "1.8.0_242" OpenJDK Runtime Environment (build 1.8.0_242-8u242-b08-0ubuntu3~18.04-b08) OpenJDK 64-Bit Server VM (build 25.242-b08, mixed mode) Thanks in advance.
