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    <p>The first thing to note in your code is this:</p> <pre><code>super("The title"); </code></pre> <p>This actually calls the <code>JFrame</code> constructor, and passed it <code>"The title"</code> as a title String. This is an explicit example of using the <code>Jframe</code> functionality in your code. This will build the window that appears for you.</p> <p>Using methods like <code>add</code> are all inherited from the <code>JFrame</code> class. These add <code>Components</code> to the JFrame object.</p> <p><b> Why Inheritance? </b></p> <p>Well, simply, your class IS a JFrame, with a little more. When you have a <code>Is A</code> operation, you use inheritance. The other advantage of this method is that your class can be referred to as a JFrame. That is:</p> <pre><code>JFrame tuna = new tuna(); // Note: All classes are meant to start with a capital letter. </code></pre> <p><b> Another viewpoint </b></p> <p>It's important to note that you don't strictly HAVE TO inherit from a JFrame class. You can use <code>Composition</code>. In this instance you'd have something like:</p> <pre><code> public class Tuna { private JFrame parentWindow; // Rest of class. } </code></pre> <p>As mentioned above, the convention is to follow the <code>Is A</code> and <code>Has A</code> approach. If class <code>A</code> Is an example of class <code>B</code>, we tend to use inheritance. If class <code>A</code> has an instance of class <code>B</code>, then you use composition, although in most cases, inheritance is interchangeable with Composition.</p> <p><b> Another another Viewpoint </b></p> <p>As mentioned in the comments, you should always look for an existing API that offers this kind of functionality, before attempting to implement it yourself.</p>
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    1. POWhy do we need to extend JFrame in a swing application?
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    1. COI have one more question. When I am writing `JFrame tuna = new tuna();` am I creating object of JFrame class or am I referring the `tuna` class as a JFrame
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      1. USWizard Sultan
    2. CO@AmlanKarmakar: you are doing both. You are creating a tuna object (which should be named "Tuna" since it's a class) but since Tuna extends JFrame, it also *is a* JFrame. It is being held by a JFrame *variable* though and so the variable will not be able to reference any new methods that aren't already part of JFrame. 1+ to Chris's decent answer by the way.
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      1. USHovercraft Full Of Eels
    3. CO@HovercraftFullOfEels Learn something new every day!
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