Java checked exception not in the function's throw specification?

Question

Normally, the Java compiler confirms that all checked exceptions that are thrown are in the throw specification. Does anything special happen when a native function throws a java checked exception that was not in the functions throw specification list, or does is the throw specification list simply ignored at runtime?

C++

void function(JNIEnv * env, jclass jc) {
    jclass newExcCls = env->FindClass("java/lang/NullPointerException");
    env->ThrowNew(newExcCls, "ERROR");
}

Java

public class Tester {
    static {
        System.loadLibrary( "MyLibrary" );
    }        
    private static native void function();
    public static void main(String [ ] args) {
        try {
            function();
        } catch( Exception e ) { //is it caught? Or what happens?
            e.printStackTrace();
        }        
    }
}

(The C++ function name would probably be mangled. Also loadLibrary should be in a try catch. Don't care, I don't believe it's relevant to the problem. There's possibly other errors in the code, but they're probably not relevant either.)

I'm kinda surprised this isn't a duplicate. – Mooing Duck Aug 01 '12 at 21:37 — Mooing Duck, Aug 01 '12 at 21:37

score 5 · Accepted Answer · answered Aug 01 '12 at 19:57

5

You don't even have to resort to native code to fool the checked exception mechanism. See the Javadoc on Thread.stop(Throwable). I was once left wondering for the entire day how my code threw an InterruptedException in the middle of code that did not declare it. I didn't even find the answer then, but now I know :)

Answering your immediate question: yes, the checked exception logic is a compiler-only feature and ignored at runtime.

answered Aug 01 '12 at 19:57

Marko Topolnik

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The function you linked is not a great example, since it only throws unchecked exceptions as far as I can see, which do not have to be in the throw specification list. – Mooing Duck Aug 01 '12 at 20:43
Read the following sentence, then: "The thread represented by this thread is forced to complete whatever it is doing abnormally and to throw the Throwable object obj as an exception." – Marko Topolnik Aug 01 '12 at 20:45
Oh, missed that sentance, I was looking for Exception class names. Interesting find. – Mooing Duck Aug 01 '12 at 20:57

Java checked exception not in the function's throw specification?

1 Answers1