Invoking method from String

Hello,

I have this code (it does compile)

Code:

---

import java.lang.reflect.*;

public class Example
{

    private final Object waitObj = new Object();

    public static void main(String[] args) {
        new Example();
    }
   
    private Example() {
        waitForState(waitObj,getMethod(this,"initialized"));
        System.out.println("Done");
    }

    private void waitForState(final Object waitObj, final Method method) {
        try {
            synchronized (waitObj) {
                while ((new Boolean(true)).equals(method.invoke(method.getDeclaringClass(),new Object[] {})))
                    waitObj.wait();
            }
        }
        catch (Exception e) {
            e.printStackTrace();
        }
    }

    private Method getMethod(final Object obj, final String method) {
        try {
            return obj.getClass().getMethod(method,new Class[]{});
        }
        catch (Exception e) {
            e.printStackTrace();
            return null;
        }
    }
   
    public boolean initialized() {
        return true;
    }

}

---

I want it to wait until the method initialized() returns true.

This throws the following error:

Quote:

---

java.lang.IllegalArgumentException: object is not an instance of declaring class

---

How to fix this? If possible

What is Misc?

Code:

---

public class Example
{   
    public static void main(String[] args) {
        frame = new MyFrame(this);

---

What's this, then?

Post a SSCCE - something brief that actually yields the compiler message you mention when anyone tries to compile it.

MyFrame is a frame that extends JFrame - but that's not really important. Misc is the class where the getMethod method is in -not really important either, i guess.

This is the waitforstate method (in misc)

Code:

---

public static void waitForState(final Object waitObj, final Method method) {
        try {
            synchronized (waitObj) {
                while ((new Boolean(true)).equals(method.invoke(method.getDeclaringClass(),new Object[] {})))
                    waitObj.wait();
            }
        }
        catch (Exception e) {
            error(e);
        }
    }

---

where does your illegal argument exception get thrown? Is it inside waitForState or inside getMethod?

Which method is throwing the exception: look at the stack trace.

Quote:

---

My trouble is in the method 'Misc.getMethod(Object,String)'

---

That method ^

Well nothing in that method declares itself as throwing that exception, and no-one can test it because the code you've provided won't compile.

I suppose you've made a point there.

Main post edited, compilable code.

As the stack trace tells you, the exception is actually thrown by Method.invoke() in Example.waitForState()

You have to call a method on the actual object, not an instance of Class.

I'm afraid you lost me there - what should I change?
has it something to do with this in the waitforstate method?

Code:

---

method.getDeclaringClass()

---

Yes, read the API docs for Method.invoke().

The real question is why are you using reflection to do all this, instead of just calling initialised() directly?

Code:

---

while (!obj.initialised()) {
    obj.wait();
}

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Because I want it to work for any boolean method. ;)