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Thread: method calling

  1. #1
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    Question method calling

    What would the code:

    stack.top().getX() do? I mean, what would it call?

    a.) call the getX() method of the result result by stack.top()
    b.) call the getX() method of stack, which doesn't exist

    When should I use:

    stack.top().getX()

    and when should I use :

    (stack.top()).getX()

    ?


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    Member DavidFongs's Avatar
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    Default Re: method calling

    It will call the getX() of whatever top() returns

    The two examples at the end of your post would have identical results

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    javapenguin (November 3rd, 2010)

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    Default Re: method calling

    Quote Originally Posted by javapenguin View Post
    and when should I use :

    (stack.top()).getX()

    ?
    You only need parentheses if you need to cast the value returned by stack.top() to a Type that has the method getX().

    For example, in GUI coding an event has a getSource() method that returns Object. If you know what subclass of Object is the source of the event, you can cast it accordingly to use its methods.
    public void actionPerformed(ActionEvent e) {
      ((JButton) e.getSource()).setIcon(...);
    }
    // equivalent to
    actionPerformed(ActionEvent e) {
      Object o = e.getSource();
      JButton button = (JButton) o;
      button.setIcon(...);
    }
    db

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    javapenguin (November 4th, 2010)

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