How do I make the method return type generic?

Question

Consider this example (typical in OOP books):

I have an Animal class, where each Animal can have many friends.
And subclasses like

Answer 1

As the question is based in hypothetical data here is a good exemple returning a generic that extends Comparable interface.

public class MaximumTest {
    // find the max value using Comparable interface
    public static > T maximum(T x, T y, T z) {
        T max = x; // assume that x is initially the largest

        if (y.compareTo(max) > 0){
            max = y; // y is the large now
        }
        if (z.compareTo(max) > 0){
            max = z; // z is the large now
        }
        return max; // returns the maximum value
    }    


    //testing with an ordinary main method
    public static void main(String args[]) {
        System.out.printf("Maximum of %d, %d and %d is %d\n\n", 3, 4, 5, maximum(3, 4, 5));
        System.out.printf("Maximum of %.1f, %.1f and %.1f is %.1f\n\n", 6.6, 8.8, 7.7, maximum(6.6, 8.8, 7.7));
        System.out.printf("Maximum of %s, %s and %s is %s\n", "strawberry", "apple", "orange",
                maximum("strawberry", "apple", "orange"));
    }
}