Generic Comparable type for compareTo

Question

I have a method called getMember which may return any Comparable object, String, Integer etc. I can't figure out what to use as type parameter so compareTo will work. Code below is not working

Comparable<? extends Comparable<?>> m1 = column.getMember(o1);
Comparable<? extends Comparable<?>> m2 = column.getMember(o2);

int compareTo = m1.compareTo(m2);

In case I wasn't clear, m1 and m2 will always be same type. Comparing without type parameters works fine, I just wanted to know what to put in <>

Answer 1

I think what you need here is a generic method. Whatever method this section of code is in must be generified. Here's my best shot, in absence of your source for the getMember method.

public <T extends Comparable<? super T>> void doSomethingTheOPWants() {
    ...
    T m1 = column.getMember(o1);
    T m2 = column.getMember(o2);
    int compareTo = m1.compareTo(m2);
}

With my current knowledge of the code, I don't think I can create a relevant/worthwhile test, so I'll leave that up to OP.