BufferStrategy questions

I'm trying to understand this code, tell me if my considerations are correct

//bs is a BufferStrategy object

public void gameLoop()
{ 
    do
    {
        do
        {
             Graphics g=null;
             try
                 {
                     g=bs.getDrawGraphics();
                     g.clearRect(0,0,getWidth(),getHeight());
                     render(g);
                 }
             finally
             {
                 if(g!=null)
                 {
                     g.dispose();
                 }
             }
        }
        while(bs.contentsRestored());
        bs.show();
     }
    while(bs.contentsLost());
}

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    The getDrawGraphics give me a buffer zone where write , the render method create the frame in that space.
    If the frame is correctly create the dispose method releases system resources by the buffer zone.
    The contentsRestored() is called due a lost and it implies that the frame have to be redrawn.
    The contentsLost is not clear to me...