ADDITIONAL SYSTEM INFORMATION :
same result on different hardware and Windows 7

A DESCRIPTION OF THE PROBLEM :
paint works fine for versions up to 1.8.0_192 but degrades on recent versions e.g. 11.0.1.
paint method take 60(!) times longer to complete.

REGRESSION : Last worked in version 8u192

STEPS TO FOLLOW TO REPRODUCE THE PROBLEM :
compile and run using jdk1.8.0_192
(compile and ) run using jdk-11.0.1

EXPECTED VERSUS ACTUAL BEHAVIOR :
EXPECTED -
similar performance for jdk1.8.0_192 and jdk-11.0.1

ACTUAL -
jdk-11.0.1 takes 60 times longer than jdk1.8.0_192


---------- BEGIN SOURCE ----------
import java.awt.*;
import java.awt.event.*;

class GraphicsPaintPerformance extends Frame // javax.swing.JFrame
{
   int [] x = null;
   int [] y = null;
   
   public static void main( String [] args )
   {
      new GraphicsPaintPerformance();
   }
   
   GraphicsPaintPerformance()
   {
      int N = 20000;
      x = new int[N];
      y = new int[N];
      
      for( int i = 0; i < N; i++ )
      {
         x[i] = (int)( 500 * Math.random() + 50 );
         y[i] = (int)( 500 * Math.random() + 80 );
      }
      
      setSize( 600, 630 );
      setVisible( true );
      
      addWindowListener( new WindowAdapter()
      {
         public void windowClosing( WindowEvent we )
         {
            System.exit(0);
         }
      });
   }
   
   public void paint( Graphics g )
   {
      long start = System.currentTimeMillis();
      
      int n = x.length;
      for( int i = 1; i < n; i++ )
      {
         g.drawLine( x[i-1], y[i-1], x[i], y[i] );
      }
      
      g.setColor( Color.WHITE );
      g.fillRect( 250, 280, 100, 100 );
      
      
      g.setColor( Color.BLACK );
      g.drawString( 0.001 * ( System.currentTimeMillis() - start ) + " s", 280, 335 );
   }
}
---------- END SOURCE ----------

CUSTOMER SUBMITTED WORKAROUND :
stay with jdk1.8.0_192

FREQUENCY : always