[SOLVED] Use enum that implements interface as parameter as key in EnumMap

Use enum that implements interface as parameter as key in EnumMap

I want to have a family of child classes that extend BaseClass, which has in turn a EnumMap defined. Depending on the IDE I plug this code in. It tells me that the Constructor

EnumMap<B, Integer>()

is not defined, respectively B is not within the specified bounds.

interface A {}
enum B implements A {hello, world}

abstract class BaseClass {
    protected EnumMap<? extends A, Integer> baseMap;
}

class ChildClass extends BaseClass {
    public ChildClass () {
        baseMap = new EnumMap<B,Integer>();
    }
}

E.g. the third last line gives me troubles. I don't see what is wrong.

Solution

EnumMap takes the enum in the constructor:

baseMap = new EnumMap<B,Integer>(B.class);

And as we're in a post Java 7 world

baseMap = new EnumMap<>(B.class);

I would suggest using a Map in the declaration - program to the interface:

protected Map<? extends A, Integer> baseMap;