Question

I have lots of object defined in the system, perhaps 1000 objects,
and some of them have this method:

public Date getDate();

Is there anyway I can do something like this:

Object o = getFromSomeWhere.....;

Method m = o.getMethod("getDate");
Date date = (Date) m.getValue();

Answer 1

If you can make them all implement an interface, that would certainly be the best option. However, reflection will also work, and your code was nearly there:

Object o = getFromSomeWhere.....;
Method m = o.getClass().getMethod("getDate");
Date date = (Date) m.invoke(o);

(There’s a bunch of exceptions you’ll need to handle, admittedly…)

For a full example:

import java.lang.reflect.*;
import java.util.*;

public class Test
{
    public static void main(String[] args) throws Exception
    {
        Object o = new Test();
        Method m = o.getClass().getMethod("getDate");
        Date date = (Date) m.invoke(o);
        System.out.println(date);
    }

    public Date getDate()
    {
        return new Date();
    }
}