import java.awt.*;

/**
 * SupplyRow starts with fixed list of Box's and gives them away,
 * is not a process
 */
public class SupplyRow extends Row { 
    public SupplyRow (Rectangle loc, Canvas canvas) {
	super (loc, canvas);

	// Our initial set of boxes
	for (int i=0; i<22; i++) {
	    boxes.add (new Box ());
	}
    }

    /**
     * Give away one of our boxes
     * Need a single, "synchronized" routine
     * that reports whether we have any to give
     * AND takes it ("test and set")
     * So this routine tries to give a box,
     * returns the Box if succeeds, or null if fails
     */
    public synchronized Box take() { 
	if (boxes.size()>0) { 
	    Box ans = boxes.remove (0); 
	    canvas.repaint (); 
	    return ans; 
	}
	else return null; 
    } 
}