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Consumer mapped Class in HashMap

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闹比i
闹比i 2020-12-03 06:19

I want to create an IdentityHashMap, Consumer>. Basically, I want to map a type with a method saying what to do with this type.

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  • 醉梦人生
    醉梦人生 (楼主)
    2020-12-03 06:49

    It is possible to implement this in a type-safe manner without any unchecked cast. The solution resides in wrapping the Consumer into a more general Consumer that casts and then delegates to the original consumer:

    public class ClassToConsumerMap {
    private final Map, Consumer> map = new IdentityHashMap<>();

    public  Consumer put(Class key, Consumer c) {
        return map.put(key, o -> c.accept(key.cast(o)));
    }

    public  Consumer get(Class key) {
        return map.get(key);
    }
}



    Depending on your needs, get() could also simply return a Consumer. This would be necessary if you only know the type at runtime, e.g.
    


    classToConsumerMap.get(someObject.getClass()).accept(someObject);

    


    I am pretty sure I saw this solution (or something similar) in a talk @ Devoxx Belgium 2016, possibly from Venkat Subramaniam, but I definitively cannot find it back…
    
    
    
             
    
                                                        
    
            
            
    
              
                
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