How do I make the method return type generic?

Question

Consider this example (typical in OOP books):

I have an Animal class, where each Animal can have many friends.
And subclasses like

Answer 1

There are a lot of great answers here, but this is the approach I took for an Appium test where acting on a single element can result in going to different application states based on the user's settings. While it doesn't follow the conventions of OP's example, I hope it helps someone.

public  T tapSignInButton(Class type) throws NoSuchMethodException, IllegalAccessException, InvocationTargetException, InstantiationException {
    //signInButton.click();
    return type.getConstructor(AppiumDriver.class).newInstance(appiumDriver);
}

• MobilePage is the super class that the type extends meaning you can use any of its children (duh)
• type.getConstructor(Param.class, etc) allows you to interact with the constructor of the type. This constructor should be the same between all expected classes.
• newInstance takes a declared variable that you want to pass to the new objects constructor

If you don't want to throw the errors you can catch them like so:

public  T tapSignInButton(Class type) {
    // signInButton.click();
    T returnValue = null;
    try {
       returnValue = type.getConstructor(AppiumDriver.class).newInstance(appiumDriver);
    } catch (Exception e) {
        e.printStackTrace();
    }
    return returnValue;
}