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Problem with Generic

 
Alex Kruglov
Greenhorn
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Hi, everyone!

I have a following code:


When I'm trying to implement this interfaces, for example this way:

I'm getting an error at line 21: type parameter BigDecimalResult is not within its bounds

Does anyone know what could be the problem?

Thanks in advance!
 
Rob Spoor
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The problem is that Task's generic type is <T extends TaskResult<T>>. BigDecimalResult does not implement TaskResult<BigDecimalResult> but TaskResult<BigDecimal>. If you change the declaration to "interface Task<T extends TaskResult<?>>" it will compile. Another option is to use two generic types:
This does make it messy, and you only need it if you need the T of TaskResult.
 
Alex Kruglov
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Thanks, Rob!
It's what I needed to know.
 
Rob Spoor
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You're welcome.
 
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