int[] oneDim = new int[]{1,2,3};
int[][] twoDim = new int[][]{{1,2,3},{4,5,6},{7,8,9}};
int[][] weirdButLegal = new int[][]{null, oneDim, oneDim , twoDim[1],{7,8,9,10,11,12,13,14,15}};

BufferedImage img = gc.createCompatibleImage( 640, 480 );  //whole screen buffer
while (true){
    Graphics gfx = img.getGraphics();
    gfx.setColor(Color.BLACK);
    gfx.fill(640,480);  //oops, image content altered..., VRAM cache discarded if present.
    int x = rand.nextInt(256);
    int y = rand.nextInt(256);
    gfx.setColor(Color.BLUE);
    gfx.fillRect(x,y,50,50);  //draw blue box in random location on large image
    gfx.dispose();
    Graphics bufGfx = bufferStrategy.getDrawGraphics();
    bufGfx.drawImage(img,0,0,null);  //draw large image, always modified since last draw, must copy from system RAM to VRAM
    bufGfx.dispose();
    bufferStrategy.show();
    // sleep, yield, etc...
}

BufferedImage img = gc.createCompatibleImage( 50,50 );  //small image of a blue box, so only 50x50.
Graphics gfx = img.getGraphics();
gfx.setColor(Color.BLUE);
gfx.fillRect(0,0,50,50);  //image is rendered only once.
gfx.dispose();
while (true){
    Graphics bufGfx = bufferStrategy.getDrawGraphics();
    bufGfx.setColor(Color.BLACK);
    bufGfx.fill(640,480);  // direct call on buffer, accelerated by DirectX or OpenGL
    int x = rand.nextInt(256);
    int y = rand.nextInt(256);
    bufGfx.drawImage(img,x,y,null);  //draw small image at random location.  image not modified, so quick copy from VRAM is possible
    bufGfx.dispose();
    bufferStrategy.show();
    // sleep, yield, etc...
}

long targetFPS = 100;
long maximumNanosPerFrame = TimeUnit.SECONDS.toNanos(1) / targetFPS;  // at 100 FPS, should be 10M
while (running){
    long frameStartTime = System.nanoTime();
    updateGameLogic();
    renderToScreen();
    long elapsedNanosThisFrame = System.nanoTime() - frameStartTime;
    long nanosTillNextFrame = maximumNanosPerFrame - elapsedNanosThisFrame;
    if (nanosTillNextFrame > 0)
        try {
            TimeUnit.NANOSECONDS.sleep( nanosTillNextFrame ); 
       } catch (InterruptedException ie) { 
            System.out.println("weird, got interrupted while sleeping.  Spurious interruption on Solaris or Linux maybe? Ignoring.");
       }
    else
        System.out.println("Probable stutter.  Frame took too long, overrun by " + ( - nanosTillNextFrame) );
}

                            int j = 0;
                            for (; j < dist; j++)
                            {
                                int xx = xt * j / 120 + 120;
                                int yy = yt * j / 120 + 120;
                                int xm = xx + xCam - 120;
                                int ym = yy + yCam - 120;

                                if (map[(xm + ym * 1024) & (1024 * 1024 - 1)] == 0xffffff) break;

                                int xd = (xx - 120) * 256 / 120;
                                int yd = (yy - 120) * 256 / 120;

                                int ddd = (xd * xd + yd * yd) / 256;
                                int br = brightness[ddd] * brr / 255;

                                if (ddd < 16)
                                {
                                    int tmp = 128 * (16 - ddd) / 16;
                                    br = br + tmp * (255 - br) / 255;
                                }

                                lightmap[xx + yy * 240] = br;
                            }

        gl.glViewport(0, 0, 640, 480); //viewport typically matches size of screen/canvas
        gl.glMatrixMode(GL.GL_PROJECTION);
        gl.glLoadIdentity();
        glu.gluOrtho2D(-320, 320, -240, 240); //some multiple of screen/viewport dimensions to preserve aspect ratio and prevent squashing

a.subList(start,end).clear();