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Editorial Team
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Asked: 2026-05-14T00:18:19+00:00

class Bouncy<T> extends Throwable { } // Error: the generic class Bouncy<T> may not

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class Bouncy<T> extends Throwable {     
}
// Error: the generic class Bouncy<T> may not subclass java.lang.Throwable

Why doesn’t Java support generic Throwables?

I realize that type erasure complicates certain things, but obviously Java gets by with a lot already, so why not push it one more notch and allow generic Throwables, with comprehensive compile-time check for potential problems?

I feel like the type erasure argument is rather weak. Currently, we can’t do:

void process(List<String> list) {
}

void process(List<Integer> list) {
}

Of course, we get by without it. I’m not asking that we should be able to do catch Bouncy<T1> and Bouncy<T2> in the same try block, but if we use them in disjoint contexts with strict compile-time enforceable rules (which is pretty much the way generics works right now), wouldn’t it be workable?

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1 Answer

  1. Editorial Team

    Java Language Specification
    8.1.2 Generic Classes and Type Parameters:

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

    Personally, I think it’s because we can’t get any benefits of generics inside a catch clause. We can’t write catch (Bouncy<String> ex) due to type erasure, but if we write catch (Bouncy ex), it would be useless to make it generic.

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