What will happen in Java when I use a method of the super class which has not been written?

Consider the Java code below, what would happen if there were no paintComponent method in JPanel class?

...

import javax.swing.JPanel;

public class ShapesJPanel extends JPanel
{

     public void paintComponent( Graphics g )
     {
   开发者_运维问答    super.paintComponent( g );
       //more codes here  
     }
}

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It won't compile. If it was there at compile time but not at runtime, then it will throw an Error.

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1. If that's the specific situation you're asking about then it's always there.
2. If you're asking in general then it won't compile.

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There will always be an implementation in the super class.

JPanel implements paintComponent(). So, you don't need to worry about it.

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At compile time

• The method should present in any of the class in super class hierarchy otherwise compilation will fail

• The method of the class from that hierarchy ( starting from bottom) will get called

At run time

• If method does not found it will throw an error