Java – How do I create a callback (added as a dynamic parameter, a function)?

I’m creating this method/function and I need to implement the callback. I mean, I need to add a function as a dynamic parameter.
I’ve read several articles but I don’t understand how to get it.
Any ideas or examples of use?

public void httpReq (final String url, final Object postData, String callbackFunct, Object callbackParam,String callbackFailFunct) {
    if (postData == null || postData == "") {
        GET
        Thread testGET = new Thread(new Runnable() {
            @Override
            public void run() {
                StringBuilder builder = new StringBuilder();
                HttpClient client = new DefaultHttpClient();
                HttpGet httpGet = new HttpGet(url);
                ....
                }
        }
    } else {
        POST
        Thread testPOST = new Thread(new Runnable() {
            @Override
            public void run() {
                HttpGet httpPost = new HttpPost(url);
                ....
                }
        }
    }
}

Define your interface:

public interface MyInterface {
  public void myMethod();
}

Add it as a parameter to your method

public void httpReq (final String url, final Object postData, String callbackFunct, Object callbackParam,String callbackFailFunct, MyInterface myInterface) {
     when the condition happens you can call myInterface.myMethod();
}

When you call your method, for example

myObjec.httpReq(url, postData, callbackFunct, callbackParam, callbackFailFunct,
 new MyInterface() {
     @Override
     public void myMethod() {

}
 });

Is this what you need?