How to add two enums to a single Map object as key and value

Question

I have two enums. I would like to create a Map object out of the two enums.

I have gone through EnumMap but it says only the key can be an enum. Please correct me if i am wrong.

private enum Export {
    BINGOEXPORT, DEFECTSEXPORT, IBC3EXPORT, IBCONTRACTSEXPORT, 
    RMAHEADEREXPORT, RMALINESEXPORT, SITESEXPORT, SREXPORT
};

private enum Preperation {
    BINGOPREPERATION, DEFECTSPREPERATION, IBC3PREPERATION, 
    IBCONTRACTSPREPERATION, RMAHEADERPREPERATION, RMALINESPREPERATION, 
    SITESPREPERATION, SRPREPERATION, IBEXPORTLOGPREPERATION
};

Answer 1

A normal HashMap works fine to have the enum as a key and value.

Map<Export, Preparation> myMap = new HashMap<>();
myMap.put(Export.BINGOEXPORT, Preparation.BINGOPREPERATION);

Answer 2

If you would like to use one enum as the key and the other one as a value, EnumMap allows you to do that ( demo ):

EnumMap<Export,Preparation> e2p = new EnumMap<Export,Preparation>(Export.class);
e2p.put(Export.RMALINESEXPORT, Preparation.SRPREPERATION);
System.out.println(e2p.get(Export.RMALINESEXPORT));

If you would like to mix enum s as keys of the same Map , one approach is to make a common interface for the two enum s, and use it as the key type for your Map . You can do it because Java enum s are allowed to extend classes and implement interfaces:

private interface CommonKey {
    int hashCode();
    boolean equals(Object other);
}

private enum Export implements CommonKey {
    BINGOEXPORT, DEFECTSEXPORT, IBC3EXPORT, IBCONTRACTSEXPORT, RMAHEADEREXPORT, RMALINESEXPORT, SITESEXPORT, SREXPORT
}

private enum Preperation implements CommonKey {
    BINGOPREPERATION, DEFECTSPREPERATION, IBC3PREPERATION, IBCONTRACTSPREPERATION, RMAHEADERPREPERATION, RMALINESPREPERATION, SITESPREPERATION, SRPREPERATION, IBEXPORTLOGPREPERATION
}

Now you can declare your map:

Map<CommonKey,SomeClass> myMap = new HashMap<>();
myMap.put(Export.BINGOEXPORT, someObject);
myMap.put(Preperation.RMAHEADERPREPERATION, antherObject);

Both interface methods are optional, because they are inherited from java.lang.Object . I added them to the interface anyway, to make it easier for your readers to understand what parts of the implementing classes are important for your use of the interface.

Answer 3

您可以尝试制作两个实现相同接口的枚举