Question

The problem i’m having is that javac thinks T doesnt implement compareTo(). So how can i do this while still staying “generic”. Wouldnt casting to specific type defeat the purpose of using generic type?

public class Tree<T> implements Comparable<T> {

    private T value;


    public T getValue() {
        return value;
    }

    @Override
    public int compareTo(T arg0) {
        // TODO Auto-generated method stub
        if (this.getValue() != null) {
            return this.getValue().compareTo(arg0);        // compilation problem
        }
    }
}

Answer 1

You need to refine the generic type argument to Tree<T extends Comparable<T>> — otherwise the compiler has no idea that your T object has a compareTo(T t) method defined for it.