Question

So I have been reading a tutorial on Android development, and I have come across something that I have never seen during my Java developing (mainly school work):

Thread th = new Thread() { 
    public void run() {
        if (iotdHandler == null) {
            iotdHandler = new IotdHandler(); 
        }
        iotdHandler.processFeed(); resetDisplay(
        iotdHandler.getTitle(), 
        iotdHandler.getDate(),
        iotdHandler.getUrl(),
        iotdHandler.getDescription());
        dialog.dismiss();
    }
};
th.start();

Now the book says extend thread, and I kind of understand what its doing, in a sense, but it doesn’t follow the usual way to extend a normal class in java like so:

public Class Dog extends Animal...

and then you can follow on and override methods and such. But my question is, what is it actually doing in making a reference to new Thread object, but at the same time creating a method right after it, and what I assume is overriding some sort of method in the Thread class? Since I do not know what it is called, I can’t really search for it, so I apologize for the obvious question if it is one. Any help would be much appreciated.

Answer 1

Revise your Java books 🙂 It’s called an anonymous inner class and was originally introduced to facilitate Java GUI development (with AWT/Swing). Since Android UI development follows many of the same patterns, it is used quite often in Android.

What it does is instantiating a class in place (without defining it in a separate file, etc.), overriding some of its methods (int this case run()). You can also implement an interface this by if you provide implementations for all of its methods.