Egge: New page: In response to [http://nat.truemesh.com/archives/000738.html Generic Throws: Another Little Java Idiom] Unfortunately, the "X extends Exception" falls apart fairly quickly with the curren...

2008-06-26T12:16:29Z

New page: In response to [http://nat.truemesh.com/archives/000738.html Generic Throws: Another Little Java Idiom] Unfortunately, the "X extends Exception" falls apart fairly quickly with the curren...

New page

In response to [http://nat.truemesh.com/archives/000738.html Generic Throws: Another Little Java Idiom]

Unfortunately, the "X extends Exception" falls apart fairly quickly with the current generation of type erasure. You can get a little way down this path, but soon you'll hit string compile errors, which go away, depending on the order in which you compile / recompile things. The problem is two fold:
# Java has type erasure
# RuntimeException extends Exception, but doesn't have to be declared in a throws clause.

So, the compiler may or may not be able to determine if a method throws a typed exception.

If this technique worked, it would be useful for implementing closure like features. For example:

<geshi lang="java">
public interface BlockBase<I, O, X extends Throwable> {
O eval(I item) throws X;
}

public <X extends Throwable> RArray<T> findAll(BlockBase<T, Boolean, X> block) throws X {
RArray<T> arr = new RArray<T>();
for (T t : this) {
if (block.eval(t)) {
arr.append(t);
}
}
return arr;
}
</geshi>

You'll notice in code like [http://gee.cs.oswego.edu/dl/jsr166/dist/jsr166ydocs/jsr166y/forkjoin/package-summary.html fork-join] framework, they rely wholly on unchecked exceptions.

[[Category:Java]]

X extends Exception - Revision history

Egge: New page: In response to [http://nat.truemesh.com/archives/000738.html Generic Throws: Another Little Java Idiom] Unfortunately, the "X extends Exception" falls apart fairly quickly with the curren...