repaint() in Java [duplicate]
If you added JComponent to already visible Container, then you have call frame.getContentPane().validate(); frame.getContentPane().repaint(); for example import java.awt.Color; import java.awt.Dimension; import java.awt.Graphics; import javax.swing.JFrame; import javax.swing.JLabel; import javax.swing.JOptionPane; public class Main { public static void main(String[] args) { JFrame frame = new JFrame(); frame.setSize(460, 500); frame.setTitle(“Circles generator”); frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE); SwingUtilities.invokeLater(new Runnable() { public void run() { … Read more