Question

I’m just wondering if it’s possible to invoke a method by reflection inside a thread. My idea is to pass to the thread constructor a method name so that is how I would like to specify what the thread should do (which method should be run). The code below is not working – I obtain an error “ClassNotFoundException”.

public class Listener extends Thread {

    /** Constructor */
    private static Window win = new Window();
    private static Class c;

    private String parameter;

    public Listener(String param) {
        this.parameter = param;
    }

    public void run() {
        try {
            Class c = Class.forName("Listener");
            Class partypes[] = new Class[1];
            partypes[0] = String.class;
            Method meth = c.getMethod("waitForWindowAppear", partypes);
            Listener methobj = new Listener(parameter);
            Object arglist[] = new Object[1];
            arglist[0] = parameter;

            Object retobj = meth.invoke(methobj, arglist);
            Integer retval = (Integer) retobj;
            System.out.println(retval.intValue());
        } catch (Exception e) {
            e.printStackTrace();
        }
    }

    /** Method waits as a thread for window at class or title */
    private static void waitForWindowAppear(String title) {
        while (true) {
            try {
                Thread.sleep(1000);
            } catch (InterruptedException exc) {
                System.out.println("Thread waitForWindowAppear has been stoped!");
                return;
            }
            if (win.isWindowVisible(title)) {
                // System.out.println("Window found!");
                return;
            } else {
                // System.out.println("Waiting for window!");
            }
        }
    }
}

Do anyone have some ideas how to solve this problem?

Answer 1

I would say you don’t have this class Listener on your Default package, therefore, what you should do is use the fully qualified name, for example:

Class c = Class.forName("foo.bar.Listener");

The ClassNotFoundException is thrown because it doesn’t find Listener class, and one reason would be the incomplete name.

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Additionally, you use getMethod, this will not work with private methods, please use getDeclaredMethod instead.

From documentation:

getMethod – Returns a Method object that reflects the specified public
member method of the class or interface represented by this Class
object.

getDeclaredMethod – Returns a Method object that reflects the
specified declared method of the class or interface represented by
this Class object.