check parent-child loop function-CodePudding

I'm trying to create a function that can recognize the parent-child loop.
Imagin

Object A is a parent of Object B
Object B is a parent of Object C

create a function that can prevent the parent-child loop. the function should give at least two parameters (childName, parentName) and get errors if the relationship creates a loop. in the above example if we pass (A, C) should print or pass string:

"A is the parent of C"

I know how to create this function(you can provide answer with any language):

private static void restrict_ParentChild_Loop(Object A, Object B) throws Exception {
    if (A.parent == null)
        return;
    if (A.parent.equals(B)) {
        throw new Exception("");
    } else {
        restrict_ParentChild_Loop(A.parent, B);
    }
}

My main question is about how to provide the right message in the Exception. ("A is the parent of C")

CodePudding user response：

My main question is about how to provide right message in the Exception.

I'm still wondering why that's not the question title itself.

Since this question is likely opinion-based... I'll give my shot?

Your code at:

throw new Exception("");

Will throw an Exception like this:

java.lang.Exception: At ...

So it will be even better if you just tell it what you want it to show in the first place:

throw new Exception(A.parent " is the parent of " B.child);
//This throws:
java.lang.Exception: A is the parent of C: At ...

Which results in:

private static void restrict_ParentChild_Loop(Object A, Object B) throws Exception {
    if (A.parent == null)
        return;
    if (A.parent.equals(B)) {
        throw new Exception(A.parent " is the parent of " B.child);
    } else {
        restrict_ParentChild_Loop(A.parent, B);
    }
}