What's the point of a copied / duplicate reference variable?

I just saw the following code:

public static void initElements(WebDriver driver, Object page) {
    final WebDriver driverRef = driver;
    initElements(new DefaultElementLocatorFactory(driverRef), page);
}

Can somebody tell me, what's the advantage of writing this instead of:

public static void initElements(WebDriver driver, Object page) {
    initElements(new DefaultElementLocatorFactory(driver), page);
}

I hope my first question here isn't too pointless and/or stupid and youi have fun answering it!

(Code quote f开发者_Go百科rom org.openqa.selenium.support.PageFactory; Copyright 2007-2009 WebDriver committers; Copyright 2007-2009 Google Inc.)

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There's no difference in application behavior. However such pattern might be used when:

• wanting to provide a local name of the value which is better suited in this context. Here it's driverRef vs driver, which doesn't bring any value, but in other cases it might
• wanting to make the variable accessible as a local variable for debugger. Debuggers may treat local variables and class fields differently (e.g. when presenting their values), but it's hard to justify such a change to be made permamently
• caring of readability. Here the replaced expression is simple - just driver, but sometimes you have a more complicated expression which would make the line too long if inlined.

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In this case I don't see any point. But I can see a point to declare variable as final. So this is going to be sufficient:

public static void initElements(final WebDriver driver, Object page) {
    initElements(new DefaultElementLocatorFactory(driver), page);
}

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I think the 'final' keyword is the answer to your question.

final means the reference cannot be reassigned.

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As already said, in the code you posted there's really no point.

One reason for making a variable final is when you want to use it in an anonymous inner class inside the method. A variable must be final to be able to be accessed inside the anonymous inner class. A somewhat silly example, just to illustrate the point:

public static void initElements(final WebDriver driver, final Object page) {
    // Anonymous inner class
    Runnable runnable = new Runnable() {
        @Override
        public void run() {
            // The variables must be final, otherwise you can't access them here
            initElements(new DefaultElementLocatorFactory(driver), page);
        }
    };

    runnable.run();
}