How to Change the Border of a JFrame in Java

In this tutorial, we are going to see how to change the border of a JFrame in Java. You can draw borders around an undecorated JFrame. Just get the root panel of the JFrame and set its borders with the method setBorder(Border border).
 

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First remove the frame decoration:

frame.setUndecorated(true);

Then draw the border:

frame.getRootPane().setBorder(
        BorderFactory.createMatteBorder(4, 4, 4, 4, Color.BLUE)
);

 
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Java Program to Change the Border of a JFrame:

import java.awt.*;
import javax.swing.*;

public class BorderFrameExample extends JFrame 
{
   JLabel l = new JLabel("Welcome to StackHowTo!", JLabel.CENTER);
   
   public BorderFrameExample() {
      //add label to frame
      add(l, BorderLayout.CENTER);
      //remove the decoration
      setUndecorated(true);
      //set border
      getRootPane().setBorder(
         BorderFactory.createMatteBorder(4, 4, 4, 4, Color.BLUE)
      );
      setSize(250,250);
      setVisible(true);
      setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
   }
   public static void main(String[] args) {
      new BorderFrameExample();
   }
}

Output:

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