Question

In this example the asString() invocations do not compile. (Aside: Invoking toString() does compile but I need to customize.) How do I invoke asString, or any method, of a generic type, given that the method has in fact been provided for every possible T?

class Range<T>
{
    private T min;
    private T max;

    Range(T min, T max)
    {
        this.min = min;
        this.max = max;
    }  

    String makeString()
    {
        return "The range is from " + min.asString() + " to " + max.asString();
    }
}

Answer 1

You need to provide an interface that has asString method defined, for example:

interface AsStringable {
    String asString();
}

Then define your class like this:

class Range<T extends AsStringable>
{
    private T min;
    private T max;

    Range(T min, T max)
    {
        this.min = min;
        this.max = max;
    }  

    String makeString()
    {
        return "The range is from " + min.asString() + " to " + max.asString();
    }
}