Generics in return types

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kelvSYC - 13 Dec 2007 16:08 GMT

One application of generics is probably in a return type, for example

public class Delegate<Ret> {
public Ret dothis() {
// ...
}
}

This of course implies that something is to be returned. Now, this
has probably been asked before, but what is a safe way to simulate a
void delegate? Would it be to do something like:

public class VoidDelegate extends Delegate<Void> {
public Void dothis() {
// ...
return null; // Void is non-instanced, so that's the only
thing we can return
}
}

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RedGrittyBrick - 13 Dec 2007 16:54 GMT

> One application of generics is probably in a return type, for example
>
[quoted text clipped - 15 lines]
> }
> }

I came across this recently with SwingWorker. From memory, Eclipse
objected to every Void/void combo I tried except for

new SwingWorker<Void, Void>() {
protected Void doInBackground() {
...
return null;
}
protected void done() {
...
}
}

Note the use of small-v void and no return for done().
This seems odd to me but maybe someone can make sense of it?

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kelvSYC - 13 Dec 2007 17:43 GMT

> Note the use of small-v void and no return for done().
> This seems odd to me but maybe someone can make sense of it?

That's because done() javax.swing.SwingWorker is not generic.

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Generics in return types

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