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POWhy do we need to extend JFrame in a swing application?
 

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  1. POWhy do we need to extend JFrame in a swing application?
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    <p>Why do we need to extend the <code>JFrame</code> class when building a Swing application. As far as I know <code>extends</code> is used for inheriting the base class. None of the functions of the <code>JFrame</code> class are used in the following program but still it is extended. I know I am missing out on some information. Is it like some of the functions of JFrame class are running in the background.</p> <p>1) Code</p> <pre><code>import java.awt.Container; import java.awt.FlowLayout; import java.awt.event.ActionListener; import java.awt.event.ActionEvent; import javax.swing.JFrame; import javax.swing.JTextField; import javax.swing.JPasswordField; import javax.swing.JOptionPane; public class tuna extends JFrame{ private JTextField item1; private JTextField item2; private JTextField item3; private JPasswordField passwordField; Container contentPane ; public tuna(){ super("The title"); setLayout(new FlowLayout()); item1 = new JTextField(10); contentPane.add(item1); item2 = new JTextField("enter text here"); add(item2); item3 = new JTextField("uneditable", 20); item3.setEditable(false); add(item3); passwordField = new JPasswordField("mypass"); add(passwordField); thehandler handler = new thehandler(); item1.addActionListener(handler); item2.addActionListener(handler); item3.addActionListener(handler); passwordField.addActionListener(handler); } public static void main(String[] args){ tuna aye = new tuna(); } private class thehandler implements ActionListener{ public void actionPerformed(ActionEvent event){ String string = ""; if(event.getSource()==item1) string=String.format("field 1: %s",event.getActionCommand()); else if (event.getSource()==item2) string=String.format("field 2: %s",event.getActionCommand()); else if (event.getSource()==item3) string=String.format("field 3: %s",event.getActionCommand()); else if (event.getSource()==passwordField) string=String.format("password field is: %", event.getActionCommand()); } } } </code></pre>
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    1. COThe premise of this question is false. You don't have to extend a JFrame in order to use it.
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    2. COactually, you should _not_ extend a JFrame (nor any other class except when you really enhance functionality, that is implement something that can't be achieved by using/configuring that class) - most tutorials and Netbeans are giving bad examples :-)
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