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

public class SwingHelloWorld {
public static void main(String[] args) {

JFrame frame = new JFrame("Hello World Java Swing");
// set frame site
frame.setMinimumSize(new Dimension(400, 300));
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
// center the JLabel
JLabel label = new JLabel("Hello World!", SwingConstants.CENTER);
// add JLabel to JFrame
frame.getContentPane().add(label);
// display it
frame.pack();
frame.setVisible (true);
}
}