This example shows how to draw a white rectangle on a black background using JOGL. The example is ported from C examples in the OpenGL Programming Guide (known as the "red book").

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 package glredbook11;

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

import javax.media.opengl.*;

/**
 * This is a simple, introductory OpenGL program in Java using the
 * javax.media.opengl extension library.
 *
 * @author Kiet Le (Java conversion)
 */
public class hello
  extends JFrame
    implements GLEventListener
{
  private GLCapabilities caps;
  private GLCanvas canvas;

  //
  public hello()
  {
    super("hello");

    /*
     * display mode (single buffer and RGBA)
     */
    caps = new GLCapabilities();
    caps.setDoubleBuffered(false);
    System.out.println(caps.toString());
    canvas = new GLCanvas(caps);
    canvas.addGLEventListener(this);
    //
    getContentPane().add(canvas);
  }

  /*
   * Declare initial window size, position, and set frame's close behavior. Open
   * window with "hello" in its title bar. Call initialization routines.
   * Register callback function to display graphics. Enter main loop and process
   * events.
   */
  public void run()
  {
    setSize(512, 256);
    setLocationRelativeTo(null); // center
    setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
    setVisible(true);
  }

  public static void main(String[] args)
  {
    new hello().run();
  }

  public void init(GLAutoDrawable drawable)
  {
    GL gl = drawable.getGL();

    /* select clearing color (background) color */
    gl.glClearColor(0.0f, 0.0f, 0.0f, 0.0f);

    /* initialize viewing values */
    gl.glMatrixMode(GL.GL_PROJECTION);
    gl.glLoadIdentity();
    gl.glOrtho(0.0, 1.0, 0.0, 1.0, -1.0, 1.0);
  }

  public void display(GLAutoDrawable drawable)
  {
    GL gl = drawable.getGL();

    /* clear all pixels */
    gl.glClear(GL.GL_COLOR_BUFFER_BIT);

    /*
     * draw white polygon (rectangle) with corners at (0.25, 0.25, 0.0) and
     * (0.75, 0.75, 0.0)
     */
    gl.glColor3f(1.0f, 1.0f, 1.0f);
    gl.glBegin(GL.GL_POLYGON);
    gl.glVertex3f(0.25f, 0.25f, 0.0f);
    gl.glVertex3f(0.75f, 0.25f, 0.0f);
    gl.glVertex3f(0.75f, 0.75f, 0.0f);
    gl.glVertex3f(0.25f, 0.75f, 0.0f);
    gl.glEnd();

    /*
     * don't wait! start processing buffered OpenGL routines
     */
    gl.glFlush();

  }

  public void reshape(GLAutoDrawable drawable, int x, int y, int width,
      int height)
  {
    GL gl = drawable.getGL();
  }

  public void displayChanged(GLAutoDrawable drawable, boolean modeChanged,
      boolean deviceChanged)
  {
  }

}

Source: Kiet Le's The Red Book Examples using JOGL