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Have fixed parameters in Java constructor - possible?

I've defined an object in Java - as far as the Java is concerned, they're the same thing, but as far as the data which populates them is concerned, they can be one of three types (wildly named 1,2,3 with 0 for the "root").
What I'd really like to be able to do is have four constructors defined, as they need slightly different params for each type. I could do it with strategic nulls, but it seems like the wrong thing to do. What I'd love to have is something like:

public MenuNode(int type = 1, param1, param2, param3) {
    doStuffHere();
} 
public MenuNode(int type = 2, paramX, paramY) {
    doStuffHere();
}

and then call something along the lines of:

switch (toQueue.itemType) {

    when ITEM_TYPE_STATIC {
        MenuNode mn1 = new MenuNode(ITEM_TYPE_STATIC, param1, param2, param3);
    }

    when ITEM_TYPE_DYNAMIC {
        MenuNode mn2 = new MenuNode(ITEM_TYPE_DYNAMIC, paramX, paramY);
    }

}

etc etc.

I hope this makes some sort of sense - it's a bit out there, and Googling only comes up with references to public static void etc. If someone with a bit more experience/know-how with Java than me can take a look, eternal love and gratitude will be forthcoming.

like image 343
Morris Fauntleroy Avatar asked Mar 24 '26 01:03

Morris Fauntleroy


2 Answers

Another approach is to avoid using a constructor here, and create a static factory method which calls a private constructor:

class MenuNode {
    private MenuNode() {
        // Does nothing important
    }
    public static MenuNode createStatic(param1, param2, param3) {
         MenuNode result = new MenuNode();
         result.setItemType(ITEM_TYPE_STATIC);
         result.setParam1(param1);
         result.setParam2(param2);
         result.setParam3(param3);
         result.doStuffHere();
         return result;
    }
    public static MenuNode createDynamic(paramX, paramY) {
         MenuNode result = new MenuNode();
         result.setItemType(ITEM_TYPE_DYNAMIC);
         result.setParamX(paramX);
         result.setParamY(paramY);
         result.doStuffHere();
         return result;
    }
like image 92
Adrian Cox Avatar answered Mar 26 '26 13:03

Adrian Cox


If I understood your scenario right, you may want to thing about refactoring this approach.

Make MenuNode a base class, and inherit your subtypes from it (MenuNodeType1, MenuNodeType2 etc.). That way you'll get control over the single types but you can still throw them all into one collection.

like image 35
Bobby Avatar answered Mar 26 '26 13:03

Bobby



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